Chapter 06: Genetics

Ibsen: Oral Pathology for the Dental Hygienist, 7th Edition

Multiple Choice

1. Which statement is correct concerning chromosomes?

a. Chromosomes are located in the of the cell.

b. Mature germ cells (ova and spermatozoa) contain 46 chromosomes.

c. Chromosomes can only be seen clearly under a microscope when the nucleus and cell are dividing.

d. Chromosomes contain RNA, which directs the production of amino acids, polypeptides, and proteins by the cell.

ANS: C

Chromosomes can only be seen clearly under a microscope when the nucleus and cell are dividing. At other times the genetic material is dispersed in the nucleus. Chromosomes are located in the nucleus of the cell. They contain the hereditary units called genes that are transmitted from one generation to another. Each cell of the human body, with the exception of mature germ cells, has 46 chromosomes. Half of these chromosomes are derived from the father and the other half from the mother. Chromosomes contain DNA, which directs the production of amino acids, polypeptides, and proteins by the cell.

REF: Chromosomes, page 188 OBJ: 1

2. The gap 2 (G2) phase of mitosis a. begins when mitotic division ends. b. ends when mitotic division begins. c. precedes the S phase. d. is when replication of DNA takes place.

ANS: B

The G2 phase of mitosis ends when mitotic division takes place and follows the S phase. Replication of DNA takes place in the S phase. The gap 2 (G2) phase of mitosis ends when mitotic division begins. The G2 phase of mitosis follows the S phase. Replication of DNA takes place during the S phase.

REF: Mitosis, page 188 OBJ: 2

3. The correct order for the stages of mitosis is a. prophase, anaphase, metaphase, telophase. b. prophase, metaphase, anaphase, telophase. c. prophase, metaphase, telophase, anaphase. d. metaphase, prophase, telophase, anaphase.

ANS: B

The correct order for the stages of mitosis is prophase, metaphase, anaphase, telophase. During prophase the chromosomes are lining up toward metaphase; in metaphase, the chromosomes stain intensely and are arranged almost symmetrically at both sides of the center of the cell; in anaphase and telophase the chromatids are in the process of splitting. Metaphase occurs before anaphase during mitosis. Anaphase occurs before telophase during mitosis. Prophase is the first stage of mitosis, and anaphase occurs before telophase.

REF: Stages of Mitosis, page 188 OBJ: 2 a. 23; diploid b. 46; haploid c. 23; haploid d. 46; diploid

4. Primitive germ cells have _____ chromosomes and are termed _____.

ANS: D

Primitive germ cells have 46 chromosomes and are called diploid, with two chromosomes for each pair. Meiosis is a two-step special type of cell division in which the primitive germ cells reduce their chromosome number by half and become mature germ cells. Primitive germ cells have 46 rather than 23 chromosomes. Primitive germ cells are called diploid rather than haploid. Primitive germ cells have 46 chromosomes and are called diploid.

REF: Meiosis, page 189 OBJ: 3

5. Points of contact between the chromatid of one chromosome and the chromatid of the other chromosome of a pair, where crossing over and exchange of chromosome segments occur are termed a. first meiosis. b. second meiosis. c. chiasmata. d. interpolation.

ANS: C

Points of contact between the chromatid of one chromosome and the chromatid of the other chromosome of a pair, where crossing over and exchange of chromosome segments occur, are called chiasmata. This special aspect of the first meiosis takes place at metaphase. Crossing over occurs during first meiosis, but the contacts between pairs of chromosomes occur at chiasmata. Crossing over occurs during first meiosis; the second stage of meiosis is essentially a mitotic division in which each chromosome splits longitudinally. Crossing over and exchange of chromosome segments occur at the chiasmata, not interpolation.

REF: First Meiosis, page 189 OBJ: 3

6. After metaphase of the first meiotic division a. the chromosomes split at the centromere and separate from one another. b. the chromosomes do not split at the centromere but separate from one another. c. each member of the pair migrates to one of the new cells, each of which contains 46 chromosomes but twice the final amount of DNA. d. each member of the pair migrates to one of the new cells, each of which contains 23 chromosomes but half the final amount of DNA.

ANS: B

After metaphase of the first meiotic division, the chromosomes do not split at the centromere but separate from one another. Each member of the pair migrates to one of the new cells, each of which contains 23 chromosomes but twice the final amount of DNA. After metaphase of the first meiotic division, the chromosomes do not split at the centromere but separate from one another. Each member of the pair migrates to one of the new cells, each of which contains 23 rather than 46 chromosomes but twice the final amount of DNA. Each member of the pair migrates to one of the new cells, each of which contains 23 chromosomes but twice rather than half the final amount of DNA.

REF: First Meiosis, page 190 OBJ: 3 a. Oogenesis starts around the time of puberty. b. The second meiosis is completed at the beginning of ovulation. c. Nondisjunction is more prevalent in male spermatogenesis than in female oogenesis. d. The older the woman, the greater the chance of shedding a trisomic ovum.

7. Which statement is true of oogenesis?

ANS: D

The older the woman, the greater the chance of shedding a trisomic ovum. Oogenesis starts around the third month of prenatal life, and the future ova remain in suspended crossing-over from about the time of birth until the time ovulation starts. The first meiosis rather than second meiosis is completed at the beginning of ovulation. Nondisjunction is more prevalent in female oogenesis than in male spermatogenesis.

REF: First Meiosis, page 190 OBJ: 3

8. Features of second meiosis include a. a replication of DNA before initiation. b. essentially a mitotic division in which each chromosome splits longitudinally. c. formation of four cells from the parent cell. d. the formation of 2n DNA.

ANS: B

Features of second mitosis include essentially a mitotic division in which each chromosome splits longitudinally. Replication of DNA does not occur before the second meiosis. After splitting, two cells rather than four are formed from the parent cell. The second mitosis results in the formation of two cells from the parent cell, each containing 1n DNA.

REF: Second Meiosis, page 190 OBJ: 3

9. According to the Lyon hypothesis during the early period of embryonic development, the a. genetic activity of both of the X chromosomes in each cell of a female embryo is inactivated. b. genetic activity of one of the X chromosomes in each cell of a female embryo is inactivated. c. genetic activity of the Y chromosome in each cell of a male embryo is inactivated. d. inactivated chromosome forms a structure known as the pronucleus.

ANS: B

According to the Lyon hypothesis, during the early period of embryonic development, the genetic activity of one of the X chromosomes in each cell of a female embryo is inactivated. The genetic activity of one of the two X chromosomes in each cell of a female embryo is inactivated. The genetic activity of one of the two X chromosomes in each cell of a female embryo rather than the genetic activity of the Y chromosome in each cell of a male embryo is inactivated. The inactivated chromosome forms a structure known as the Barr body. The Barr body appears as a dark dot at the periphery of the nucleus.

REF: Lyon Hypothesis, page 190 OBJ: 4

10. In DNA a sequence of thymine, adenine, and cytosine (TAC) is always matched by a. adenine, cytosine, and guanine (ACG). b. guanine, adenine, and cytosine (GAC). c. adenine, thymine, and guanine (ATG). d. a five-carbon sugar and a phosphate.

ANS: C

In DNA a sequence of thymine, adenine, and cytosine (TAC) is always matched by adenine, thymine, and guanine (ATG). The base adenine is always bound to the base thymine, and guanine is always bound to cytosine. Thymine, adenine, and cytosine (TAC) are always matched by adenine, thymine, and guanine (ATG). Thymine, guanine, and cytosine would be matched by adenine, cytosine, and guanine (ACG). Thymine, adenine, and cytosine (TAC) are always matched by adenine, thymine, and guanine (ATG). Cytosine, thymine, and guanine would be matched by guanine, adenine, and cytosine (GAC). The basic unit of DNA is called a nucleotide, which is formed by a nitrogen-containing base, a five-carbon sugar, and a phosphate.

REF: Deoxyribonucleic Acid, page 190 OBJ: 1

11. During translation a. polypeptides form an amino acid, and one or more amino acids form a protein. b. amino acids form a polypeptide, and one or more polypeptides form a protein. c. proteins form a polypeptide, and one or more polypeptides form an amino acid. d. amino acids form a protein, and one or more proteins form a polypeptide.

ANS: B

During translation, amino acids form a polypeptide, and one or more polypeptides form a protein. During translation, amino acids form a polypeptide, and one or more polypeptides form a protein. During translation, amino acids form a polypeptide, and one or more polypeptides form a protein. During translation, amino acids form a polypeptide, and one or more polypeptides form a protein

REF: Deoxyribonucleic Acid, pages 190-191

OBJ: 1 a. mRNA b. tRNA c. rRNA d. hnRNA

12. Which type of RNA carries the message for translation of DNA to ribosomes in the cytoplasm?

ANS: A mRNA carries the message for transcription of DNA to ribosomes in the cytoplasm. tRNA transfers amino acids from the cytoplasm to the mRNA, positioning amino acids in the proper sequence to form polypeptides and subsequent proteins. rRNA combines with several polypeptides to form ribosomes. hnRNA is found within the nucleus. It is the precursor of mRNA.

REF: Types of Ribonucleic Acid, page 191 OBJ: 1

13. Genes that are located at the same level in homologous chromosomes and that dictate the same functions or characteristics are termed a. consanguineous. b. chromatids. c. alleles. d. precocious.

ANS: C

Genes that are located at the same level in homologous chromosomes and that dictate the same functions or characteristics are called alleles. Genes that are located at the same level in homologous chromosomes and that dictate the same functions or characteristics are called alleles, not consanguineous. Genes that are located at the same level in homologous chromosomes and that dictate the same functions or characteristics are called alleles, not chromatids. Genes that are located at the same level in homologous chromosomes and that dictate the same functions or characteristics are called alleles, not precocious.

REF: Genes and Chromosomes, page 192

14. If both loci for blood are AO, the a. person is said to have blood group O. b. person is said to have blood group A. c. person would be homozygous. d. characteristic is recessive.

ANS: B

OBJ: 1

If both loci for blood are AO, the person is said to have blood group A. Only if both loci are empty does the person have blood group O. When the allelic genes are identical, the person is said to be homozygous for that gene or a homozygote. When the genes are different, the person is said to be heterozygous for that gene or a heterozygote. If a gene can express its effect clinically with a single dose (heterozygous), as in the combination AO (which equals blood group A), the characteristic is dominant. If the gene needs a double dose to exhibit its action (homozygous), the resulting characteristic is said to be recessive.

REF: Genes and Chromosomes, page 192

15. Which is true about making a karyotype?

OBJ: 1 a. Arginine may be used to arrest the mitosis of leukocytes at metaphase. b. Colchicine may be used to arrest the mitosis of leukocytes at metaphase. c. Colchicine may be used to arrest the mitosis of red blood cells at anaphase. d. It is used to evaluate molecular abnormalities in chromosomes.

ANS: B

In making a karyotype colchicine may be used to arrest the mitosis of leukocytes at metaphase. A karyotype may use colchicine rather than arginine to arrest the mitosis of leukocytes at metaphase. In making a karyotype colchicine may be used to arrest the mitosis of leukocytes rather than red blood cells at metaphase. A karyotype is used to evaluate gross abnormalities in chromosomes. Molecular alterations occur at the DNA level and are not detectable microscopically.

REF: Chromosomal Abnormalities, page 193

OBJ: 1 a. Aneuploidy is a complete second set of chromosomes, meaning a total of 46. b. Polyploidy is any number of chromosomes that do not represent an exact multiple of the total chromosome complement. c. Euploidy is a complete second set of chromosomes, meaning a total of 46. d. Aneuploidy may be represented by trisomy and monosomy.

16. Which statement is true regarding gross chromosomal abnormalities involving alterations in the number of human chromosomes?

ANS: D

Aneuploidy may be represented by trisomy (a pair with an identical extra chromosome) and monosomy (a missing chromosome from a pair). Aneuploidy is any extra number of chromosomes that do not represent an exact multiple of the total chromosome complement. Polyploidy is three or four complete sets of chromosomes. This has been described occasionally in humans and is incompatible with life. Euploidy is a complete second set of chromosomes, the total number being 92.

REF: Gross Chromosomal Abnormalities, page 193

17. Most cases of Down syndrome are associated with a. maternal consumption of alcohol. b. late maternal age at the time of conception. c. estrogen supplements. d. inhalation of vapors from volatile substances.

ANS: B

OBJ: 5

Most cases of Down syndrome are associated with late maternal age at the time of conception. It is the most frequent of the trisomies. Most cases of Down syndrome are associated with late maternal age at the time of conception. Fetal alcohol syndrome is associated with maternal consumption of alcohol. Most cases of Down syndrome are associated with late maternal age at the time of conception, not estrogen supplements. Most cases of Down syndrome are associated with late maternal age at the time of conception, not inhalation of vapors from volatile substances.

REF: Trisomy 21, page 193

OBJ: 5 a. Trisomy 13 b. Trisomy 21 c. Turner syndrome d. Klinefelter syndrome

18. Which clinical syndrome caused by gross chromosomal abnormalities is associated with bilateral cleft lip and palate, microphthalmia or anophthalmia, and polydactyly?

ANS: A

Trisomy 13 is associated with bilateral cleft lip and palate, microphthalmia or anophthalmia, superficial hemangioma of the forehead or nape of the neck, growth retardation, severe mental retardation, polydactyly of the hands and feet, clenching of the fist with the thumb under the fingers, rocker-bottom feet, heart malformations, and several anomalies of the external genitals. Trisomy 21 is associated with slanted eyes. Patients are generally shorter than normal, and heart abnormalities are present in more than 30% of individuals. Intelligence level varies from near normal to marked retardation. Turner syndrome is characterized by a female phenotype. Clinically, these women are of short stature and have webbing of the neck and edema of the hands and feet. They frequently exhibit a low hairline on the nape of the neck. The chest is broad with wide-spaced nipples. The aorta is frequently abnormal, and body hair is sparse. Klinefelter syndrome is characterized by a male phenotype. These patients are taller than normal and have wide hips and a female pubic hair distribution. About 50% have gynecomastia, and intelligence levels are lower than normal in 10% of affected individuals.

REF: Trisomy 21, page 194 OBJ: 5 a. male; 47 b. female; 46 c. female; 45 d. male; 44

19. The majority of patients with Turner syndrome have a _____ phenotype and _____ chromosomes.

ANS: C

The majority of patients with Turner syndrome have a female phenotype, and in the majority of cases, the karyotype has the normal 44 autosomal chromosomes and only one X chromosome. A normal female would have two X chromosomes: one from the mother and one from the father. Most cases of Turner syndrome are caused by nondisjunction of the X chromosome in the paternal gamete. The majority of patients with Turner syndrome have a female rather than a male phenotype and 45 rather than 47 chromosomes. In the majority of cases, the karyotype has the normal 44 autosomal chromosomes and only one X chromosome. The majority of patients with Turner syndrome have a female phenotype and 45 rather than 46 chromosomes. In the majority of cases, the karyotype has the normal 44 autosomal chromosomes and only one X chromosome. The majority of patients with Turner syndrome have a female rather than a male phenotype and 45 rather than 44 chromosomes. In the majority of cases, the karyotype has the normal 44 autosomal chromosomes and only one X chromosome.

REF: Turner Syndrome, page 194 OBJ: 5

20. For autosomal-dominant inheritance a. males will be affected more often than females. b. the risk of having an affected offspring is 25% when a person has a gene for the condition. c. all of the offspring will be affected by a condition that is transmitted by autosomaldominant inheritance. d. an individual can carry a gene with a dominant effect without presenting any clinical manifestations.

ANS: D

For autosomal-dominant inheritance, an individual can carry a gene with a dominant effect without presenting any clinical manifestations. For autosomal-dominant inheritance, males and females are equally affected. For autosomal-dominant inheritance, the risk of having an affected offspring is 50% for each pregnancy when a person has a gene for that condition. For autosomal-dominant inheritance, genetic risk is governed by chance. None, less than half, half, more than half, or all of the offspring could be affected by a condition that is transmitted by autosomal-dominant inheritance.

REF: Autosomal-Dominant Inheritance, page 195 OBJ: 6 a. none; none b. none; all c. all; none d. all; all

21. A man’s X chromosome is transmitted to _____ of his daughters and _____ of his sons.

ANS: C

A man’s X chromosome is transmitted to all of his daughters and none of his sons. The X chromosome in his sons comes from the mother. Consequently, no male-to-male transmission of X-linked traits occurs.

REF: X-Linked Inheritance, page 195 OBJ: 6

22. A mother who is a carrier of an X-linked recessive trait has a 50% risk of giving birth to a(n) a. affected son or daughter. b. carrier son or daughter. c. affected son or a carrier daughter. d. carrier son or an affected daughter.

ANS: C

A mother who is a carrier of an X-linked recessive trait has a 50% risk of having an affected son or a carrier daughter. Both daughters and sons have a 50% risk of getting the X chromosome with the gene for that condition.

REF: X-Linked Inheritance, page 195 OBJ: 7 a. It is inherited as an X-linked dominant condition. b. It is inherited as a Y-linked recessive condition. c. All X chromosomes are abnormal in the female carrier. d. Female carriers tend to bleed more than usual after extraction of teeth or scaling and curettage.

23. Which statement is true concerning hemophilia A?

ANS: D

Female carriers tend to bleed more than usual after extraction of teeth or scaling and curettage. It is inherited as an X-linked recessive, not X-linked dominant, condition. It is inherited as an X-linked rather than a Y-linked recessive condition. Some of the canceled X chromosomes in the female carrier have the abnormal gene, and others have the normal one. The female carrier is a mosaic.

REF: Lyon Hypothesis and X-linked Recessive Traits, page 196

OBJ: 7

24. Cyclic neutropenia is a. characterized by episodes that generally persist for 21 to 27 days. b. characterized by oral manifestations consisting of severe ulcerative gingivitis or gingivostomatitis. c. caused by a deletion on the long arm of chromosome 11 regions 14-21. d. inherited as an autosomal recessive condition.

ANS: B

Cyclic neutropenia is characterized by oral manifestations consisting of severe ulcerative gingivitis or gingivostomatitis. The cycles usually occur in intervals of 12 to 27 days rather than 21 to 27 days, but in some patients, the intervals may be extended to several months. These episodes generally persist for 2 to 3 days. The gene is located on the short arm of chromosome 19. The inheritance pattern is autosomal dominant.

REF: Cyclic Neutropenia, page 196 OBJ: 8 a. Preventive antibiotic therapy is instituted to protect against secondary opportunistic infections. b. Treatment should be done when the circulating neutrophil count is low to reduce the risk of complications such as gingival hemorrhage and secondary infection. c. Dental hygiene care increases the risk of opportunistic infections in patients with cyclic neutropenia. d. Patients are treated periodically with vitamin D to reduce symptoms.

25. Which statement is true regarding management of patients with cyclic neutropenia?

ANS: A

Preventive antibiotic therapy is instituted to protect against secondary opportunistic infections. Treatment should be done when the circulating neutrophil count is normal to reduce the risk of complications such as gingival hemorrhage and secondary infection. Dental hygiene care reduces the risk of opportunistic infections in patients with cyclic neutropenia. Patients are treated periodically with granulocyte colony-stimulating factor (G-CSF) to reduce symptoms.

REF: Cyclic Neutropenia, page 196 OBJ: 8

26. Murray-Puretic-Drescher syndrome is also known as a. cherubism. b. gingival fibromatosis with multiple hyaline fibromas. c. gingival fibromatosis with hypertrichosis, epilepsy, and mental retardation syndrome. d. Laband syndrome.

ANS: B

Murray-Puretic-Drescher syndrome is also known as gingival fibromatosis with multiple hyaline fibromas. Cherubism is an inherited disorder affecting the jaw bones and facies.

Gingival fibromatosis with hypertrichosis, epilepsy, and mental retardation syndrome and Laband syndrome are all forms of gingival fibromatosis; however, Murray-Puretic-Drescher syndrome is known as gingival fibromatosis with multiple hyaline fibromas.

REF: Gingival Fibromatosis With Multiple Hyaline Fibromas, page 198

OBJ: 8

27. Cherubism a. is inherited as an autosomal-dominant disease with marked penetrance in females and variable expressivity and incomplete penetrance in males. b. most frequently involves the maxilla. c. is characterized by a unilateral facial deformity. d. reveals a typical “soap-bubble” or multilocular appearance on radiographic images.

ANS: D

Cherubism reveals a typical “soap-bubble” or multilocular appearance on radiographic images. It usually occupies the ascending ramus of the mandible and extends into the molar and premolar areas. Cherubism is inherited as an autosomal-dominant disease with marked penetrance in males and variable expressivity and incomplete penetrance in females. Cherubism most frequently involves the mandible, but the change can affect either the mandible or the maxilla. Cherubism is characterized by a bilateral facial deformity.

REF: Cherubism, page 198 OBJ: 8

28. The areas of bony radiolucency seen in cherubism a. resemble a central giant cell granuloma when seen under the microscope. b. occur in place of the teeth, and radiographs will reveal complete anodontia. c. will increase in size as the patient matures, even until the seventh or eighth decade of life. d. will resolve, leaving the patient without any sign of facial deformity later in life.

ANS: A

The areas of bony radiolucency seen in cherubism resemble a central giant cell granuloma when seen under the microscope. The bone lesions interfere with tooth development and eruption. Most of the patients with cherubism have pseudoanodontia because of delayed eruption. The size of the jaws of patients with cherubism tends to increase rapidly until about puberty and then generally remains stable. The facial deformity seen in cases of cherubism remains for life.

REF: Cherubism, page 199 OBJ: 8 a. Gardner syndrome b. Mandibulofacial dysostosis c. Ellis–van Creveld syndrome d. Cherubism

29. Which disorder affecting the jaw bones and facies is characterized by fusion of the anterior portion of the maxillary gingiva to the upper lip from canine to canine?

ANS: C

Ellis–van Creveld syndrome is characterized by fusion of the anterior portion of the maxillary gingiva to the upper lip from canine to canine. This syndrome has an autosomal-recessive inheritance pattern. The gene for this syndrome has been mapped to the short arm of chromosome 4 region 16. Gardner syndrome is characterized by the presence of osteomas in various bones, especially the frontal bones, mandible, and maxilla. Mandibulofacial dysostosis is characterized by a facies with downward sloping of the palpebral fissures, a hypoplastic nose, hypoplastic malar bones with hypoplasia or absence of the zygomatic process, abnormal and misplaced ears, and a receding chin. Cherubism is characterized by a progressive bilateral facial swelling that appears when the patient is between 2 and 4 years of age.

REF: Ellis–van Creveld Syndrome, page 199 OBJ: 9

30. A patient with Ellis–van Creveld syndrome will a. show polydactyly on the radial side of the forearm. b. be a little person. c. lack an anterior maxillary vestibular sulcus. d. lack a posterior mandibular sulcus.

ANS: C

A patient with Ellis–van Creveld syndrome will lack an anterior maxillary vestibular sulcus. A patient with Ellis–van Creveld syndrome will show polydactyly on the ulnar side of the forearm, and fingernails and toenails will be hypoplastic and deformed. Individuals affected by Ellis–van Creveld syndrome are dwarfs (different from little people) because of distal shortening of the extremities. Other skeletal anomalies include curvature of the legs and feet. A patient with Ellis–van Creveld syndrome will lack an anterior maxillary vestibular sulcus rather than a posterior mandibular sulcus.

REF: Ellis–van Creveld Syndrome, page 199 OBJ: 9 a. Hyperplastic paranasal sinuses b. Short and wide neck c. Mushroom shape of the cranium because of premature closure of the fontanelles d. Be able to approximate their shoulders to the midline

31. A patient with unilateral or bilateral aplasia of the clavicles will have which characteristics?

ANS: D

A patient with unilateral or bilateral aplasia of the clavicles will be able to approximate his or her shoulders to the midline. Various other bone anomalies can also be present. A patient with unilateral or bilateral aplasia of the clavicles will have paranasal sinuses that are lacking or hypoplastic rather than hyperplastic. A patient with unilateral or bilateral aplasia of the clavicles will have a long and narrow neck because of unilateral or bilateral aplasia or hypoplasia of the clavicles. A patient with unilateral or bilateral aplasia of the clavicles will have a cranium that develops a mushroom shape because the fontanelles remain open rather than close prematurely.

REF: Cleidocranial Dysplasia, page 200 OBJ: 9 a. Osteogenesis imperfecta b. Nevoid basal cell carcinoma syndrome c. Mandibulofacial dysostosis d. Gardner syndrome

32. Which syndrome is characterized by intestinal polyps, which become malignant at age 30 and after?

ANS: D

Gardner syndrome is characterized by intestinal polyps, which become malignant at age 30 and after. It is also known as familial colorectal polyposis. Polyposis primarily affects the colon and rectum and generally develops before puberty. Some authors recommend intestinal resection when the polyps appear because their malignant transformation into adenocarcinoma is invariable, especially with increasing age. Osteogenesis imperfecta is characterized by defective collagen and results in abnormally formed bones that fracture easily. Nevoid basal cell carcinoma syndrome is characterized by mild hypertelorism and mild prognathism, with frontal and parietal enlargement and a broad nasal root. Mandibulofacial dysostosis is characterized by a mouth that appears fishlike, with downward sloping of the lip commissures. The facies shows downward sloping of the palpebral fissures, a hypoplastic nose, hypoplastic malar bones with hypoplasia or absence of the zygomatic process, abnormal and misplaced ears, and a receding chin.

REF: Gardner Syndrome, page 200 OBJ: 9

33. Oral manifestations of nevoid basal cell carcinoma syndrome consist of multiple cysts of the jaws that are a. central giant cell granulomas. b. peripheral giant cell granulomas. c. odontogenic keratocysts. d. calcifying epithelial odontogenic tumors.

ANS: C

Oral manifestations of nevoid basal cell carcinoma syndrome consist of multiple cysts of the jaws that are odontogenic keratocysts. These cysts vary in size; they can be very large and have a marked tendency to recur after surgical removal. On occasion, an ameloblastoma arises in them as part of this syndrome. They develop as early as 5 to 6 years of age in some affected patients and interfere with normal development of the jawbones and teeth. Oral manifestations of nevoid basal cell carcinoma syndrome consist of multiple cysts of the jaws that are odontogenic keratocysts and not central giant cell granulomas. Oral manifestations of nevoid basal cell carcinoma syndrome consist of multiple cysts of the jaws that are odontogenic keratocysts and not peripheral giant cell granulomas. Oral manifestations of nevoid basal cell carcinoma syndrome consist of multiple cysts of the jaws that are odontogenic keratocysts and not calcifying epithelial odontogenic tumors.

REF: Nevoid Basal Cell Carcinoma Syndrome, page 201 OBJ: 8

34. The basic defect responsible for osteogenesis imperfecta is produced by various mutations affecting the genes that encode type I collagen, resulting in a. lack of otic ossicles. b. unilateral or bilateral aplasia or hypoplasia of clavicles. c. overgrowth of cortical bone in the midline of the palate. d. abnormally formed bones that fracture easily.

ANS: D

The basic defect responsible for osteogenesis imperfecta is produced by various mutations affecting the genes that encode type I collagen, resulting in abnormally formed bones that fracture easily. Mandibulofacial dysostosis is associated with lack of otic ossicles.

Cleidocranial dysplasia is associated with unilateral or bilateral aplasia or hypoplasia of clavicles. Torus palatinus is associated with a bony overgrowth at the midline of the hard palate.

REF: Osteogenesis Imperfecta, page 201 OBJ: 8

35. Hard, dense, cortical bone on the buccal aspect of the alveolar ridge near the maxillary first molar would be termed a a. radiolucent torus palatinus. b. radiopaque torus mandibularis. c. maxillary exotosis. d. radiolucent exostosis.

ANS: C

Hard, dense, cortical bone on the buccal aspect of the alveolar ridge the maxillary first molar would be termed a radiopaque exostosis. Exostoses are generally asymptomatic unless traumatized and may be single, multiple, unilateral, and bilateral; these occur less frequently than either palatal or mandibular tori. Torus palatinus is a radiopaque bony overgrowth that occurs at the midline of the hard palate. Torus mandibularis is a radiopaque bony overgrowth that occurs on the lingual aspect of the mandible in the area of the premolar teeth. Hard, dense, cortical bone on the buccal aspect of the alveolar ridge by the maxillary first molar would be termed a radiopaque exostosis rather than radiolucent exostosis.

REF: Maxillary Exostosis, page 202 OBJ: 8 a. Tip and anterior dorsum of the tongue b. Palate c. Gingiva d. Buccal mucosa

36. Telangiectasias of the oral mucosa for a patient with hereditary hemorrhagic telangiectasia will be especially prominent in which location?

ANS: A

Telangiectasias of the oral mucosa for a patient with hereditary hemorrhagic telangiectasia will be especially prominent on the tip and anterior dorsum of the tongue. The palate, gingiva, and buccal mucosa are often affected but to a lesser degree. Hemorrhage from sites in the oral cavity, mainly the lips and tongue, is second in frequency to epistaxis. Telangiectasias of the oral mucosa for a patient with hereditary hemorrhagic telangiectasia will be especially prominent on the tip and anterior dorsum of the tongue rather than the palate. Telangiectasias of the oral mucosa for a patient with hereditary hemorrhagic telangiectasia will be especially prominent on the tip and anterior dorsum of the tongue rather than the gingiva. Telangiectasias of the oral mucosa for a patient with hereditary hemorrhagic telangiectasia will be especially prominent on the tip and anterior dorsum of the tongue rather than the buccal mucosa.

REF: Hereditary Hemorrhagic Telangiectasia, page 203 OBJ: 8

37. Multiple mucosal neuroma syndrome includes multiple mucosal neuromas, medullary carcinoma of the thyroid gland, and a. telangiectases. b. pheochromocytoma. c. gastrointestinal polyposis. d. blue sclera.

ANS: B

Multiple mucosal neuroma syndrome includes multiple mucosal neuromas, medullary carcinoma of the thyroid gland, and pheochromocytoma. The mucosal neuromas are prominent on the lips and the anterior dorsal surface of the tongue. They generally appear in the first few years of life. Medullary carcinoma of the thyroid has been diagnosed in more than 75% of patients with this syndrome; it generally develops in the second decade of life. Metastatic lesions develop frequently, and about 20% of patients die as a consequence of metastasis. Telangiectases are a component of Osler–Rendu–Parkes Weber syndrome. Gastrointestinal polyposis is associated with Peutz–Jeghers syndrome. Blue sclera is associated with osteogenesis imperfecta.

REF: Multiple Mucosa Neuroma Syndrome, page 203 OBJ: 9

38. Early diagnosis of pheochromocytoma is imperative because of the high malignant potential of a. squamous cell carcinoma. b. basal cell carcinoma. c. thyroid carcinoma. d. osteogenic sarcoma.

ANS: C

Early diagnosis of pheochromocytoma is imperative because of the high malignant potential of thyroid carcinoma. Pheochromocytoma itself is a benign neoplasm that generally develops in ganglia around the adrenal glands. The tumor is often bilateral and is responsible for night sweats, high blood pressure, and episodes of severe diarrhea. The pheochromocytoma induces increased urinary levels of epinephrine and other substances. Early diagnosis of pheochromocytoma is imperative because of the high malignant potential of thyroid carcinoma rather than squamous cell carcinoma. Early diagnosis of pheochromocytoma is imperative because of the high malignant potential of thyroid carcinoma rather than basal cell carcinoma. Early diagnosis of pheochromocytoma is imperative because of the high malignant potential of thyroid carcinoma rather than osteogenic sarcoma.

REF: Pheochromocytoma, page 204 OBJ: 9

39. Neurofibromatosis of von Recklinghausen is characterized by a. multiple neurofibromas appearing as macules of various sizes. b. inevitable malignant transformation. c. oral involvement in about 90% of patients. d. café au lait pigmentation of the skin in 90% of patients.

ANS: D

Neurofibromatosis of von Recklinghausen is characterized by café au lait pigmentation of the skin in 90% of patients. Multiple neurofibromas, which appear as papules and growths of various sizes, are seen on the facial skin, especially the eyelids. Malignant transformation of the neurofibromas occurs in an estimated 3% to 15% of patients with neurofibromatosis. Oral involvement is seen in about 10% of patients and is characterized by single or multiple tumors at any location in the oral mucosa, the most frequent being the lateral borders of the tongue.

REF: Neurofibromatosis of von Recklinghausen, page 204 OBJ: 9 a. Osler–Rendu–Parkes Weber syndrome b. Van der Woude syndrome c. Gorlin syndrome d. Peutz–Jeghers syndrome

40. Which syndrome is characterized by multiple melanotic macular pigmentations of the skin and mucosa, which are associated with gastrointestinal polyposis?

ANS: D

Peutz–Jeghers syndrome is characterized by multiple melanotic macular pigmentations of the skin and mucosa, which are associated with gastrointestinal polyposis. Osler–Rendu–Parkes Weber syndrome is also known as hereditary hemorrhagic telangiectasia. Van der Woude syndrome consists of cleft lip-palate and congenital lip pits. Gorlin syndrome is also known as nevoid basal cell carcinoma syndrome.

REF: Peutz–Jeghers Syndrome, page 204

41. Intestinal polyps seen with Peutz–Jeghers syndrome are

OBJ: 10 a. associated with inevitable malignant transformation into adenocarcinomas. b. hamartomas. c. caused by the adenomatous polyposis coli (APC) gene located on the long arm of chromosome 5. d. associated with osteomas in various bones, especially the frontal bones, mandible, and maxilla.

ANS: B

Intestinal polyps seen with Peutz–Jeghers syndrome are hamartomas. Intestinal polyps seen with Peutz–Jeghers syndrome develop mostly in the small intestine; only rarely do they undergo malignant transformation. Gardner syndrome is associated with inevitable malignant transformation of intestinal polyps into adenocarcinomas. The adenomatous polyposis coli (APC) gene responsible for Gardner syndrome is located on the long arm of chromosome 5. One of the basic components of Gardner syndrome is the presence of osteomas in various bones, especially the frontal bones, mandible, and maxilla.

REF: Peutz–Jeghers Syndrome, page 204

OBJ: 10 a. I: hypoplastic b. II: hypocalcified c. III: hypomaturation d. IV: hypoplastic–hypomaturation

42. Snow-capped amelogenesis imperfecta is a variation of type _____ amelogenesis imperfecta.

ANS: C

Snow-capped amelogenesis imperfecta is a variation of type III: hypomaturation amelogenesis imperfecta. It is characterized by a hypomaturation of the surface enamel of the occlusal third of all teeth in both dentitions. The maxillary teeth are more severely affected with this whitish discoloration. The enamel in those areas is of regular hardness and smooth. It does not fracture or chip from the crown. Snow-capped amelogenesis imperfecta is a variation of type III: hypomaturation amelogenesis imperfecta rather than type I: hypoplastic amelogenesis imperfecta. Snow-capped amelogenesis imperfecta is a variation of type III: hypomaturation amelogenesis imperfecta rather than type II: hypocalcified amelogenesis imperfecta. Snowcapped amelogenesis imperfecta is a variation of type III: hypomaturation amelogenesis imperfecta rather than type IV: hypoplastic–hypomaturation amelogenesis imperfecta.

REF: Amelogenesis Imperfecta, page 206 OBJ: 11 a. It is associated with taurodontic teeth. b. Teeth have bulbous crowns with a color that varies from opalescent brown to brownish blue. c. Large pulp chambers and root canals are seen on radiographs. d. Roots are long and thick with periapical radiopacities.

43. Which statement about the hereditary opalescent form of dentinogenesis imperfecta is true?

ANS: B

The hereditary opalescent form of dentinogenesis imperfecta is associated with teeth that have bulbous crowns with a color that varies from opalescent brown to brownish blue. Taurodontic teeth are associated with the hypoplastic–hypomaturation type of amelogenesis imperfecta. No pulp chambers or root canals are seen on radiographs of patients with the hereditary opalescent form of dentinogenesis imperfecta. Roots are short and thin with periapical radiolucencies on radiographs of patients with the hereditary opalescent form of dentinogenesis imperfecta.

REF: Dentinogenesis Imperfecta, page 206 OBJ: 12

44. The basic defect found with radicular dentin dysplasia lies in the a. stellate reticulum. b. epithelial root sheath. c. stratum intermedium. d. dental papilla.

ANS: B

The basic defect found with radicular dentin dysplasia seems to lie in the epithelial root sheath. This guides the formation of the root. The basic defect found with radicular dentin dysplasia seems to lie in the epithelial root sheath and not the stellate reticulum. The basic defect found with radicular dentin dysplasia seems to lie in the epithelial root sheath and not the stratum intermedium. The basic defect found with radicular dentin dysplasia seems to lie in the epithelial root sheath and not the dental papilla.

REF: Radicular Dentin Dysplasia, page 206 OBJ: 12

45. The primary dentition of a patient with coronal dentin dysplasia will appear a. normal. b. opaque with an amber color. c. translucent with an amber color. d. translucent with a blue color.

ANS: C

The primary dentition of a patient with coronal dentin dysplasia will appear translucent with an amber color. Radiographs show a lack of pulp chambers and small root canals. Permanent teeth present normal crown formation with normal color. Radiographs show thistle-shaped pulp chambers in single-rooted teeth and a bow tie appearance of the pulp chambers of permanent molars. The primary dentition of a patient with coronal dentin dysplasia will appear translucent with an amber color rather than normal. The primary dentition of a patient with coronal dentin dysplasia will appear translucent rather than opaque with an amber color. The primary dentition of a patient with coronal dentin dysplasia will appear translucent with an amber color rather than blue.

REF: Coronal Dentin Dysplasia, page 206

46. Hypohidrotic ectodermal dysplasia is characterized by a. hypodontia, hypotrichosis, and hypohidrosis. b. hyperdontia, hypotrichosis, and hypohidrosis. c. hypodontia, hypertrichosis, and hyperhidrosis. d. hyperdontia, hypertrichosis, and hyperhidrosis.

ANS: A

OBJ: 12

Hypohidrotic ectodermal dysplasia is characterized by hypodontia (partial anodontia), hypotrichosis (less than normal amount of hair), and hypohidrosis (abnormally diminished secretion of sweat). Some patients die of hyperthermia (greatly increased body temperature) after prolonged exposure to the sun or heavy exercise. Hypohidrotic ectodermal dysplasia is characterized by hypodontia rather than hyperdontia, hypotrichosis, and hypohidrosis. Hypohidrotic ectodermal dysplasia is characterized by hypodontia, hypotrichosis rather than hypertrichosis, and hypohidrosis rather than hyperhidrosis. Hypohidrotic ectodermal dysplasia is characterized by hypodontia rather than hyperdontia, hypotrichosis rather than hypertrichosis, and hypohidrosis rather than hyperhidrosis.

REF: Hypohidrotic Ectodermal Dysplasia, page 208

OBJ: 8 a. Hypophosphatemic vitamin D-resistant rickets b. Hypophosphatasia c. Hypohidrotic ectodermal dysplasia d. Dentin dysplasia

47. Frontal bossing, depressed nasal bridge, protuberant lips, and almost complete lack of scalp hair are characteristic of a person with which condition?

ANS: C

Frontal bossing, depressed nasal bridge, protuberant lips, and almost complete lack of scalp hair are characteristic of a person with hypohidrotic ectodermal dysplasia. The hair that is present is usually blond, short, fine, and stiff. The skin is soft, thin, and very dry. Sebaceous glands are also lacking. Hypophosphatemic vitamin D-resistant rickets is generally characterized by short stature and bowing of the legs, especially if the condition is present from childhood. Hypophosphatasia is characterized by rachitic-like changes, such as bowing of legs and multiple fractures. Radicular dentin dysplasia is characterized by radiographs that show total or partial lack of pulp chambers and root canals. Coronal dentin dysplasia is characterized by radiographs that show thistle-shaped pulp chambers in single-rooted teeth and a bow tie appearance of the pulp chambers of permanent molars. Permanent teeth may or may not have pulp stones.

REF: Hypohidrotic Ectodermal Dysplasia, page 208 OBJ: 8

48. Hypophosphatasia is characterized by a. an increase in serum alkaline phosphatase levels. b. abnormal formation of enamel and dentin. c. exfoliation of teeth without evidence of periodontal or gingival disease. d. an autosomal-dominant inheritance pattern.

ANS: C

Hypophosphatasia is characterized by exfoliation of teeth without evidence of periodontal or gingival disease. The basic defect in this condition is a decrease in serum alkaline phosphatase levels with increased urinary and plasma levels of phosphoethanolamine. Agenesis or abnormal formation of cementum in these patients leads to spontaneous premature shedding of primary teeth, especially mandibular incisors. The basic defect in hypophosphatasia is a decrease in serum alkaline phosphatase levels with increased urinary and plasma levels of phosphoethanolamine. Agenesis or abnormal formation of cementum rather than enamel and dentin in patients with hypophosphatasia leads to spontaneous premature shedding of primary teeth, especially mandibular incisors. The inheritance pattern of hypophosphatasia is autosomal-recessive rather than autosomal-dominant.

REF: Hypophosphatasia, page 208 OBJ: 8

49. Characteristic radiographic oral findings of hypophosphatemic vitamin D-resistant rickets include a. obliterated pulp chambers. b. large pulp chambers with very long pulp horns. c. normal pulp chambers with nonexistent roots. d. large pulp chambers with nonexistent pulp horns.

ANS: B

Characteristic radiographic oral findings of hypophosphatemic vitamin D-resistant rickets include large pulp chambers with very long pulp horns. In addition, the dentin exhibits pronounced cracks that extend to the dentinoenamel junction. These cracks induce fracture of the enamel with micro exposure of the pulp and subsequent pulpal infection. Characteristic radiographic oral findings of hypophosphatemic vitamin D-resistant rickets include large pulp chambers with very long pulp horns rather than obliterated pulp chambers. Characteristic radiographic oral findings of hypophosphatemic vitamin D-resistant rickets include large pulp chambers with very long pulp horns rather than normal pulp chambers with nonexistent roots. Characteristic radiographic oral findings of hypophosphatemic vitamin D-resistant rickets include large pulp chambers with very long pulp horns rather than large pulp chambers with nonexistent pulp horns.

REF: Hypophosphatemic Vitamin D-resistant Rickets, page 209

OBJ: 8

50. Pegged or absent maxillary lateral incisors a. affect the secondary but not primary dentition. b. have a prevalence of 10% in the white population. c. are accompanied by congenitally lacking premolar teeth in 10% to 20% of the population. d. are generally an autosomal-recessive trait with variable expressivity.

ANS: C

Pegged or absent maxillary lateral incisors are accompanied by congenitally lacking premolar teeth in 10% to 20% of the population. Both the primary and secondary dentition can be affected by pegged or absent maxillary lateral incisors, but mostly the latter. Pegged or absent maxillary lateral incisors are prevalent in 1% to 3% of the white population and in about 7% of the Asian population. Pegged or absent maxillary lateral incisors are generally an autosomal-dominant trait with variable expressivity.

REF: Pegged or Absent Maxillary Lateral Incisors, page 209 OBJ: 8 a. Chromosomes are located in the nucleus of the cell. b. Hereditary units called genes are found on chromosomes. c. Chromosomes can only be seen clearly under a microscope when the nucleus and cell are dividing. d. Chromosomes contain RNA, which directs the production of amino acids, polypeptides, and proteins by the cell.

51. Each statement about chromosomes is true except one. Which one is the exception?

ANS: D

Chromosomes contain DNA, which directs the production of amino acids, polypeptides, and proteins by the cell. Chromosomes are located in the nucleus of the cell. They contain the hereditary units called genes that are transmitted from one generation to another. Each cell of the human body, with the exception of mature germ cells, has 46 chromosomes. Half of these chromosomes are derived from the father, and the other half from the mother. Chromosomes can only be seen clearly under a microscope when the nucleus and cell are dividing. At other times the genetic material is dispersed in the nucleus.

REF: Chromosomes, page 188 OBJ: 1 a. First meiosis b. Second meiosis c. Mitosis d. Hypohidrosis

52. The gap 1, S, and gap 2 phases are part of what type of cell division?

ANS: C

After each cell division is completed and before the next division can occur, the cell enters the gap 1 phase, which is followed by the S phase, in which replication of the DNA takes place. The gap 2 phase follows the S phase and ends when mitotic division begins. First meiosis is part of a two-step special cell division and does not include the gap 1, S, and gap 2 phases. Second meiosis is part of a two-step special cell division and does not include the gap 1, S, and gap 2 phases. Hypohidrosis is an abnormally diminished secretion of sweat and is not part of cell division.

REF: Mitosis, page 188 OBJ: 2 a. Nondisjunction b. Chiasmata c. Translation d. Alleles

53. During meiosis, if chromosomes crossing over do not separate and both migrate to the same cell, a germ cell with an extra chromosome results. What is the term to describe this occurrence?

ANS: A

Nondisjunction occurs when chromosomes that were crossing over do not separate, and both migrate to the same cell. Points of contact between a chromatid of one chromosome and a chromatid of the other chromosome of a pair, where crossing over and exchange of chromosome segments occur, are called chiasmata. During translation, amino acids form a polypeptide, and one or more polypeptides form a protein. Genes that are located at the same level in homologous chromosomes and that dictate the same functions or characteristics are called alleles.

REF: First Meiosis, page 190 OBJ: 3

54. Inactivation of the genetic activity of one of the X chromosomes in each cell of a female embryo during the early period of embryonic development is referred to as a. Barr body. b. nucleotide. c. karyotype. d. the Lyon hypothesis.

ANS: D

This inactivation of one of the X chromosomes in a female embryo was postulated by Mary Lyon and is known as the Lyon hypothesis. The Barr body is the condensed chromatin of the inactivated X chromosome, not the concept of inactivation of its genetic activity. The nucleotide is the basic unit of DNA. A karyotype is the photomicrographic representation of a person’s chromosomal constitution arranged according to the Denver classification.

REF: Lyon Hypothesis, page 190 OBJ: 4 a. alteration in the structure b. abnormal rearrangement c. alteration in the number d. duplication

55. Euploid, polyploid, and aneuploid are all terms relating to a(n) _____ of chromosomes.

ANS: C

Euploid, polyploid, and aneuploid are all terms relating to an alteration in the number of chromosomes. Euploid, polyploid, and aneuploid are all terms relating to an alteration in the number of chromosomes and not the structure of chromosomes. Euploid, polyploid, and aneuploid are all terms relating to an alteration in the number of chromosomes and not the rearrangement of chromosomes. Duplication relates to abnormalities in chromosomal structure.

REF: Alterations in Number and Structure of Chromosomes, page 193

OBJ: 5 a. Both statements are true b. Both statements are false. c. The first statement is true; the second is false d. The first statement is false; the second is true.

56. Genetic risk is a mathematical estimate of probability governed by chance. A condition having autosomal-dominant inheritance is transmitted vertically from one generation to the next with males affected more than females.

ANS: C

The first statement is true; the second statement is false. Males and females are equally affected.

REF: Autosomal-Dominant Inheritance, page 195

OBJ: 6 a. Both the statement and reason are correct and related. b. Both the statement and reason are correct but not related. c. The statement is correct, but the reason is not. d. The statement is not correct, but the reason is correct. e. Neither the statement nor the reason is correct.

57. Genetic heterogeneity can cause amelogenesis imperfecta because of its inheritance pattern (X-linked, autosomal recessive, or autosomal dominant).

ANS: A

Genetic heterogeneity can cause amelogenesis imperfecta because of its inheritance pattern (X-linked, autosomal recessive, or autosomal dominant). Both the statement and reason are correct and related.

REF: Genetic Heterogeneity, page 196 OBJ: 7 a. Marked hyperkeratosis follows the normal contour of the gingiva. b. The free gingiva is highly affected with hyperkeratosis. c. Oral changes start in childhood and increase with age. d. Oral hyperkeratinization is bandlike and a few millimeters in width.

58. Each statement is true regarding focal palmoplantar and gingival hyperkeratosis except one. Which one is the exception?

ANS: B

In patients with focal palmoplantar and gingival hyperkeratosis, the free gingiva is not affected. Marked hyperkeratosis follows the normal contour of the gingiva in patients with focal palmoplantar and gingival hyperkeratosis. In patients with focal palmoplantar and gingival hyperkeratosis, oral changes start in childhood and increase with age. Oral hyperkeratinization is bandlike and a few millimeters in width in patients with focal palmoplantar and gingival hyperkeratosis.

REF: Focal Palmoplantar and Gingival Hyperkeratosis, page 198

OBJ: 8 a. Osler–Rendu–Parkes Weber syndrome b. Ellis–van Creveld syndrome c. Gorlin syndrome d. Peutz–Jeghers syndrome

59. Which syndrome is characterized by a fusion of the anterior portion of the maxillary gingiva to the upper lip from canine to canine?

ANS: B

Ellis–van Creveld syndrome is characterized by a fusion of the anterior portion of the maxillary gingiva to the upper lip from canine to canine. Osler–Rendu–Parkes Weber syndrome, also known as hereditary hemorrhagic telangiectasia, is characterized by multiple capillary dilations of the skin and mucous membranes. Gorlin syndrome, also known as nevoid basal cell carcinoma syndrome, is characterized by multiple cysts of the jaws that are odontogenic keratocysts. Peutz–Jeghers syndrome is characterized by multiple melanotic macular pigmentations of the skin and mucosa, which are associated with gastrointestinal polyposis.

REF: Ellis–van Creveld Syndrome, page 199 OBJ: 8 a. telophase b. metaphase c. prophase d. anaphase

60. Chromosomes line up at the equatorial plate during the _____ stage of mitosis.

ANS: B

Chromosomes line up at the equatorial plate during the metaphase stage of mitosis. During metaphase chromosomes are actually formed by two identical vertical halves, each composed of either left or right, short and long arms, and half of the centromere. The chromatids are in the process of splitting during telophase. During prophase the chromosomes are lining up toward metaphase. The chromatids are in the process of splitting during anaphase.

REF: Stages of Mitosis, page 188 OBJ: 2 a. two b. three c. four d. six

61. A codon in DNA is formed by a sequence of _____ bases.

ANS: B

A codon in DNA is formed by a sequence of three bases. It encodes an amino acid. A codon in DNA is formed by a sequence of three rather than two bases. A codon in DNA is formed by a sequence of three rather than four bases. A codon in DNA is formed by a sequence of three rather than six bases.

REF: Deoxyribonucleic Acid, page 190 OBJ: 1 a. adenine b. guanine c. cytosine d. thymine

62. Ribonucleic acid (RNA) contains uracil rather than the base _____ found in DNA.

ANS: D

RNA contains uracil rather than the base thymine found in DNA. RNA also differs from DNA in that it is usually single-stranded, and its sugar is a ribose rather than the deoxyribose found in DNA. RNA contains uracil rather than the base thymine found in DNA. It does not replace adenine. RNA contains uracil rather than the base thymine found in DNA. It does not replace guanine. RNA contains uracil rather than the base thymine found in DNA. It does not replace cytosine.

REF: Ribonucleic Acid, page 191 OBJ: 1 a. 10 b. 25 c. 50 d. 90

63. Gingival and periodontal disease has been reported in _____% of individuals with Down syndrome.

ANS: D

Gingival and periodontal disease has been reported in 90% of individuals with Down syndrome. Premature loss of teeth is seen frequently. Hypodontia, abnormally shaped teeth, and anomalies in eruption with malposition and crowding of teeth are common findings.

Gingival and periodontal disease has been reported in 90% rather than 10% of individuals with Down syndrome. Gingival and periodontal disease has been reported in 90% rather than 25% of individuals with Down syndrome. Gingival and periodontal disease has been reported in 90% rather than 50% of individuals with Down syndrome.

REF: Trisomy 21, page 193 OBJ: 5 a. Down b. Klinefelter c. Turner d. cri du chat

64. A karyotype containing XXXY indicates _____ syndrome.

ANS: B

A karyotype containing XXXY indicates Klinefelter syndrome. Down syndrome is trisomy of chromosome 21. A karyotype of XO represents Turner syndrome. Cri du chat syndrome results from a deletion on the short arm of chromosome 5.

REF: Klinefelter Syndrome, page 194 OBJ: 5 a. penetrance b. expressivity c. heterogeneity d. consanguinity

65. For autosomal-dominant inheritance, _____ pertains to the degree to which an individual is affected.

ANS: B

For autosomal-dominant inheritance, expressivity pertains to the degree to which an individual is affected. Penetrance refers to the number of individuals affected. The term heterogeneity is used when a condition has more than one inheritance pattern and differences exist in the degree of clinical manifestation for each of the inherited varieties. Consanguinity means a family relationship and is generally used to describe matings or marriages among close relatives, usually including first cousins.

REF: Autosomal-Dominant Inheritance, page 195

OBJ: 6 a. 0 b. 25 c. 50 d. 100

66. For parents who are carriers of the same recessive trait, the chance of giving birth to an affected child is _____%.

ANS: B

For parents who are carriers of the same recessive trait, the chance of having an affected child is 25%. The risk of having a homozygotic normal child is 25%, and the chance of having a heterozygotic carrier is 50% for each pregnancy. For parents who are carriers of the same recessive trait, the chance of having an affected child is 25% rather than zero. Each parent must contribute the recessive trait, and this will occur 25% of the time as a mathematic probability. For parents who are carriers of the same recessive trait, the chance of having an affected child is 25% rather than 50%. Each parent must contribute the recessive trait, and this will occur 25% of the time as a mathematic probability. For parents who are carriers of the same recessive trait, the chance of having an affected child is 25% rather than 100%. Each parent must contribute the recessive trait, and this will occur 25% of the time as a mathematic probability.

REF: Autosomal-Recessive Inheritance, page 195 a. O b. A c. B d. AB

67. Blood group _____ is an example of gene codominance.

OBJ: 6

ANS: D

Blood group AB is an example of gene codominance. A and B are dominant over O; but when A and B are allelic, the result is blood group AB in which both genes are exhibited. Blood group O is recessive. Groups A and B are dominant over O; but when A and B are allelic, the result is blood group AB in which both genes are exhibited. Groups A and B are dominant over O; but when A and B are allelic, the result is blood group AB in which both genes are exhibited.

REF: Genetic Heterogeneity, page 196 OBJ: 7 a. Cyclic neutropenia b. Papillon–Lefèvre syndrome c. Gingival fibromatosis d. Laband syndrome

68. __________ is an inherited disorder affecting the gingiva and periodontium, which is characterized by hyperkeratosis of the palms of the hands and soles of the feet.

ANS: B

Papillon–Lefèvre syndrome is an inherited disorder affecting the gingiva and periodontium, which is characterized by hyperkeratosis of the palms of the hands and soles of the feet. Cyclic neutropenia is characterized by a cyclic decrease in the number of circulating neutrophilic leukocytes. Gingival fibromatosis is a component of several inherited syndromes. The gingival hypertrophy generally develops early in life, and within a few years the teeth are completely covered. Laband syndrome is characterized by gingival fibromatosis, dysplastic or absent nails, and malformed nose and ears because of soft and pliable cartilage formation, hepatosplenomegaly, and hypoplasia of terminal phalanges of the fingers and toes with a resultant froglike appearance.

REF: Papillon–Lefèvre Syndrome, page 197

OBJ: 7 a. 0 to 0.5 b. 1.5 to 2 c. 4 to 6 d. 8 to 9

69. A patient with Papillon–Lefèvre syndrome will show a marked gingivoperiodontal inflammatory condition in the primary teeth at about _____ years of age.

ANS: B

A patient with Papillon–Lefèvre syndrome will show a marked gingivoperiodontal inflammatory condition in the primary teeth at about 1.5 to 2 years of age. It is marked by edema, bleeding, alveolar bone resorption, and mobility of teeth with consequent exfoliation. At about 8 or 9 years of age, the gingivoperiodontal destruction of the permanent dentition is repeated in the same manner as occurred in the primary dentition. All primary teeth are lost before 14 years of age. A patient with Papillon–Lefèvre syndrome will show a marked gingivoperiodontal inflammatory condition in the primary teeth at about 1.5 to 2 years of age rather than 0 to 0.5 years of age. A patient with Papillon–Lefèvre syndrome will show a marked gingivoperiodontal inflammatory condition in the primary teeth at about 1.5 to 2 years of age rather than 4 to 6 years of age. A patient with Papillon–Lefèvre syndrome will show a marked gingivoperiodontal inflammatory condition in the primary teeth at about 1.5 to 2 years of age rather than 8 to 9 years of age.

REF: Papillon–Lefèvre Syndrome, page 197

OBJ: 8 a. osteogenesis imperfecta b. mandibulofacial dysostosis c. cherubism d. cleidocranial dysplasia

70. A patient with _____ will have a mouth that appears fishlike, with downward sloping of the lip commissures.

ANS: B

A patient with mandibulofacial dysostosis will have a mouth that appears fishlike, with downward sloping of the lip commissures. The facies shows downward sloping of the palpebral fissures, a hypoplastic nose, hypoplastic malar bones with hypoplasia or absence of the zygomatic process, abnormal and misplaced ears, and a receding chin. The lower eyelids show a cleft of the outer third, with a lack of lashes medial to it. The ears may exhibit tags, which on occasion can also be seen near the angle of the mouth. Osteogenesis imperfecta is characterized by a dentinogenesis imperfecta-like condition. Primary teeth are affected in 80% of patients, whereas permanent teeth are affected in only 35% of these individuals. The crowns, roots, and pulp chambers are generally smaller than normal. Cherubism is characterized by radiographs of the jaws that show a typical “soap-bubble” or multilocular appearance, which usually occupies the ascending ramus of the mandible and extends into the molar and premolar areas. Cleidocranial dysplasia is characterized by a premaxilla that is generally underdeveloped, resulting in pseudoprognathism. These patients have many supernumerary teeth, sometimes even simulating a third dentition.

REF: Mandibulofacial Dysostosis, page 200

OBJ: 8 a. Hypertrichosis b. Deafness c. Hypertelorism d. Kyphoscoliosis

71. _________ is a consistent feature of mandibulofacial dysostosis.

ANS: B

Deafness is a consistent feature of mandibulofacial dysostosis. Hypertrichosis (excessive growth of hair) may be associated with gingival fibromatosis. Hypertelorism (increased distance between the eyes) and kyphoscoliosis (a combination of scoliosis, which is a lateral curving of the spine, and kyphosis, which is an abnormal vertical curvature of the spine) are both associated with nevoid basal cell carcinoma syndrome. Kyphoscoliosis is associated with nevoid basal cell carcinoma syndrome.

REF: Mandibulofacial Dysostosis, page 200 a. 80 b. 200 c. 800 d. 2000

72. Cases of facial clefting occur in about 1 in _____ births.

ANS: C

OBJ: 8

Cases of facial clefting occur in about 1 in 800 births. The majority of cases of facial clefting are multifactorial in origin. A large number of inherited syndromes can include cleft lip and palate or isolated cleft palate as a component. Cases of facial clefting occur in about 1 in 800 rather than 1 in 80 births. Cases of facial clefting occur in about 1 in 800 rather than 1 in 200 births. Cases of facial clefting occur in about 1 in 800 rather than 1 in 2000 births.

REF: Isolated Cleft Palate and Cleft Lip With or Without Cleft Palate, page 202

OBJ: 8 a. attached b. lingual c. buccal d. tonsillar

73. White sponge nevus is characterized by a white, corrugated, soft, folding oral mucosa always affecting _____ mucosa.

ANS: C

White sponge nevus is characterized by a white, corrugated, soft, folding oral mucosa always affecting buccal mucosa. The lesions are bilateral in most patients. The whitening is produced by a thick layer of keratin, which at times desquamates and leaves a raw mucosal surface. White sponge nevus is characterized by a white, corrugated, soft, folding oral mucosa always affecting buccal and not attached mucosa. White sponge nevus is characterized by a white, corrugated, soft, folding oral mucosa always affecting buccal and not lingual mucosa. White sponge nevus is characterized by a white, corrugated, soft, folding oral mucosa always affecting buccal and not tonsillar mucosa.

REF: White Sponge Nevus, page 205 OBJ: 9 a. hypoplastic b. hypocalcified c. hypomaturation d. hypoplastic-hypomaturation

74. The _____ type of amelogenesis imperfecta is characterized by tooth enamel that does not develop to a normal thickness because of failure of the ameloblasts to lay down enamel matrix properly.

ANS: A

The hypoplastic type of amelogenesis imperfecta is characterized by tooth enamel that does not develop to a normal thickness because of failure of the ameloblasts to lay down enamel matrix properly. The hypocalcified type of amelogenesis imperfecta is characterized by poorly calcified enamel of normal thickness. The hypomaturation type of amelogenesis imperfecta is characterized by enamel of mottled appearance but normal thickness. The hypoplastichypomaturation type of amelogenesis imperfecta is characterized by thin enamel that is yellow to brown and pitted. It is associated with taurodontic teeth.

REF: Amelogenesis Imperfecta, page 205 OBJ: 11 a. normal; normal b. normal; abnormal c. abnormal; normal d. abnormal; abnormal

75. Radicular dentin dysplasia is characterized by teeth with _____ crowns and _____ roots.

ANS: B

Radicular dentin dysplasia is characterized by teeth with normal crowns and abnormal roots.

REF: Radicular Dentin Dysplasia, page 206 OBJ: 12 a. Amelogenesis imperfecta b. Dentinogenesis imperfecta c. Taurodontism d. Dentin dysplasia

76. __________ is characterized by very large, pyramid-shaped molars with large pulp chambers.

ANS: C

Taurodontism is characterized by very large, pyramid-shaped molars with large pulp chambers. The furcation of the roots is displaced apically, and these teeth are classified according to the degree of furcation displacement. It is frequently found in Klinefelter syndrome and is associated with many other syndromes as well. Taurodontism and not amelogenesis imperfecta is characterized by very large, pyramid-shaped molars with large pulp chambers. Taurodontism and not dentinogenesis imperfecta is characterized by very large, pyramid-shaped molars with large pulp chambers. Taurodontism and not dentin dysplasia is characterized by very large, pyramid-shaped molars with large pulp chambers.

REF: Taurodontism, page 209 OBJ: 12 a. Hypoplastic b. Hypotrichosis c. Haploid d. Nondisjunction

77. Which term describes less than the normal amount of hair?

ANS: B

Hypotrichosis is the presence of less than the normal amount of hair. Hypoplastic refers to underdevelopment. Haploid is defined as having a single set of chromosomes. Nondisjunction is a term used in genetics when chromosomes that are crossing over do not separate, and therefore both migrate to the same cell.

REF: Vocabulary, page 187 OBJ: 1

78. Self-replication, or the ability to duplicate itself, is achievable by a. DNA. b. amino acids. c. meiosis. d. genetic heterogeneity.

ANS: A

DNA has the ability to duplicate itself (self-replication) where it can create exact copies of itself. Amino acids are the main components of protein. Meiosis is the two-step cellular division of the original germ cells. Genetic heterogeneity refers to having more than one inheritance pattern.

REF: Chromosomes, page 188 OBJ: 1

79. The constriction present in all chromosomes that joins the short and long arms is termed a. trisomy. b. nondisjunction. c. centromere. d. translocation.

ANS: C

Centromere is the constricted portion of the chromosome that divides the short arms from the long arms. Trisomy is a pair of chromosomes with an identical extra chromosome. Nondisjunction is a term used in genetics when chromosomes that are crossing over do not separate, and therefore both migrate to the same cell. Translocation is a portion of a chromosome attached to another chromosome.

REF: Vocabulary, page 186 OBJ: 1 a. Fissured tongue b. Gingival and periodontal disease c. Hypodontia d. Macrodontia

80. Oral manifestations seen with a person with Down syndrome include the following except one. Which is the exception?

ANS: D

Macrodontia is a rare condition and not typically seen in persons with Down syndrome. Fissured tongue is frequently seen in patients with trisomy 21, or Down syndrome. Gingival and periodontal disease has been reported in 90% of affected persons. Hypodontia is a common oral manifestation.

REF: Trisomy 21, page 193 OBJ: 5

81. Cyclic neutropenia is so named because this condition a. has more than one inheritance pattern. b. has environmental factors that participate in its cause. c. displays a decrease in the number of neutrophils that occur in cycles of 21 to 27 days. d. allows persons to carry a gene with a dominant effect without any clinical manifestations.

ANS: C

This condition is characterized by a cyclic decrease in the number of neutrophils, and the cycles usually occur in intervals of 21 to 27 days. The term genetic heterogeneity is used when a condition has more than one inheritance pattern. Multifactorial inheritance is used to describe a hereditary pattern where environmental factors participate in the cause of a condition. Cyclic neutropenia is not related to persons who carry a gene with a dominant effect.

REF: Cyclic Neutropenia, page 196 OBJ: 8 a. Chromosomes b. Neutrophils c. Phenotypes d. RNA

82. Persons with cyclic neutropenia display a decrease in the number of which circulating cells?

ANS: B

Neutrophils are white blood cells that arrive at the site of injury; a decrease in the number of circulating neutrophils is termed neutropenia. Chromosomes are structures located in the nucleus of cells. Phenotypes refer to the entire physical, biochemical, and physiologic makeup of an individual. RNA is ribonucleic acid.

REF: Cyclic Neutropenia, page 196 OBJ: 8

83. Identify the term that describes a mating or marriage between close relatives: a. Chiasmata b. Consanguinity c. Trisomy d. Translocation

ANS: B

Consanguinity means a familial relationship and is generally used to describe matings or marriages between close relatives, such as first cousins. Chiasmata is the intercrossing of chromatids of the same or homologous chromosomes that takes place at metaphase of first meiosis for the purpose of genetic recombination. Trisomy is a pair of chromosomes with an identical extra chromosome. Translocation is a portion of the chromosome attached to another chromosome.

REF: Autosomal-Recessive Inheritance, page 195 OBJ: 1 a. Both statements are true. b. Both statements are false. c. The first statement is true; the second statement is false. d. The first statement is false; the second statement is true.

84. A patient with Papillon–Lefèvre syndrome displays severe periodontal disease until the last tooth has been exfoliated. The skin manifestations of hyperkeratosis remain present for the life of the patient.

ANS: A

Both statements are true. The gingival and periodontal condition of these patients regains a normal appearance once the last tooth has been lost. The skin manifestations of hyperkeratinization of the hands and feet remain for life.

REF: Papillon–Lefèvre Syndrome, page 197 OBJ: 8 a. 10 b. 14 c. 22 d. 28

85. What age are all of the permanent teeth typically lost in a patient with Papillon–Lefèvre syndrome?

ANS: B

All permanent teeth are lost before 14 years of age with Papillon–Lefèvre syndrome.

REF: Papillon–Lefèvre Syndrome, page 197

OBJ: 8 a. Cleft palate b. Bilateral facial swelling c. Fissured tongue d. Severe mental handicap

86. Between the ages of and 4, what is the first clinical sign of cherubism?

ANS: B

The first clinical manifestation is a progressive bilateral facial swelling that appears when the patient is between the ages of and 4 years. A large number of inherited syndromes can include cleft palate, but cherubism is not one of these syndromes. Fissured tongue is not associated with cherubism. Severe mental handicap is not associated with cherubism.

REF: Cherubism, page 198 OBJ: 8 a. Teeth fail to erupt. b. Teeth demonstrate increased mobility. c. Increased supernumerary teeth d. Teeth exfoliate prematurely.

87. Multiple osteomas and odontomas seen with Gardner syndrome can cause which oral complication?

ANS: A

Osteomas are present in various bones with Gardner syndrome, especially the frontal bones, maxilla, and mandible. Multiple odontomas also occur in the jaws, and teeth may exhibit hypercementosis and fail to erupt. Mobility is not an oral manifestation associated with Gardner syndrome. Increased supernumerary teeth may occur in a patient with cleidocranial dysplasia. Teeth do not exfoliate prematurely in a patient with Gardner syndrome.

REF: Gardner Syndrome, page 200 OBJ: 8 a. Floor of the mouth b. Labial commissures c. Palate d. Lateral borders of the tongue

88. Where is the most common intraoral site for the development of neurofibromas in a patient with von Recklinghausen disease?

ANS: D

Tumors may arise at any intraoral location, the most frequent being the lateral borders of the tongue. Single or multiple tumors may arise at any location in the oral cavity; the tumors are not seen on the floor of the mouth. It is rare to see neurofibromas at the labial commissures. Neurofibromas rarely develop along the palatal tissues.

REF: Neurofibromatosis of von Recklinghausen, page 204 OBJ: 8 a. Café au lait pigmentation of the skin b. Spider-like telangiectases on the lips, eyelids, and nose c. Abnormally formed bones that fracture easily d. Blue sclera

89. In addition to the development of the neurofibromas, what is the prominent clinical manifestation seen with a patient with von Recklinghausen disease?

ANS: A

Café au lait pigmentation of the skin is present from the first decade of life in 90% of patients with neurofibromatosis. Spider-like telangiectases are clinically evident in a patient with hereditary hemorrhagic telangiectasia. Abnormally formed bones that fracture easily are a clinical manifestation of a patient with osteogenesis imperfecta. Blue sclerae is also seen in patients with osteogenesis imperfecta.

REF: Neurofibromatosis of von Recklinghausen, page 204

OBJ: 8 a. Amelogenesis imperfecta b. Osteogenesis imperfecta c. Hypohidrotic ectodermal dysplasia d. Dentin dysplasia

90. Your patient presents with hypodontia, hypohidrosis, and nearly complete lack of sweat and sebaceous glands. Also noticeable is a lack of eyelashes and eyebrows. Which hereditary condition is present?

ANS: C

The major components of hypohidrotic ectodermal dysplasia include: hypodontia, hypotrichosis, hypohidrosis, lacking of sweat and sebaceous glands, thin hair, soft skin, and a lack of eyelashes and eyebrows. Amelogenesis imperfecta are a group of inherited conditions affecting the enamel of teeth and having no associated systemic defects. The basic defect of osteogenesis imperfecta is produced by poor collagen, which results in abnormally formed bones that fracture easily. Dentin dysplasia typically displays teeth with short roots, lack of pulp chambers, and multiple periapical radiolucencies.

REF: Hypohidrotic Ectodermal Dysplasia, page 208

Matching

OBJ: 8 a. Autosomes b. Gamete c. Locus d. Mutation e. Phenotype f. Syndrome

For each genetic definition below, select the corresponding genetic term from the list provided.

1. Set of signs or symptoms occurring together

2. Position occupied by a gene on a chromosome

3. Nonsex chromosomes that are identical for men and women

4. Permanent change in the arrangement of genetic material

5. The observable appearance of an individual

6. Spermatozoon or ovum

1. ANS: F REF: Vocabulary, page 187

2. ANS: C REF: Vocabulary, page 187

3. ANS: A REF: Vocabulary, page 186

4. ANS: D REF: Vocabulary, page 187

5. ANS: E REF: Vocabulary, page 187

6. ANS: B REF: Vocabulary, page 187

OBJ: 1

OBJ: 1

OBJ: 1

OBJ: 1

OBJ: 1

OBJ: 1 a. Characterized by multiple abnormalities in various organs b. Down syndrome as a result of nondisjunction c. Nondisjunction of the X chromosome in the paternal gamete d. Deletion on the short arm of chromosome 5 e. Fertilized ovum has two X chromosomes plus a Y chromosome

For each clinical syndrome below, select the corresponding chromosomal abnormality from the list provided.

7. Cri du chat

8. Trisomy 13

9. Klinefelter

10. Turner

11. Trisomy 21

7. ANS: D

REF: Clinical Syndromes Resulting From Gross Chromosomal Abnormalities, page 195

OBJ: 5

8. ANS: A

REF: Clinical Syndromes Resulting From Gross Chromosomal Abnormalities, page 194

OBJ: 5

9. ANS: E

REF: Clinical Syndromes Resulting From Gross Chromosomal Abnormalities, page 194

OBJ: 5

10. ANS: C

REF: Clinical Syndromes Resulting From Gross Chromosomal Abnormalities, page 194

OBJ: 5

11. ANS: B

REF: Clinical Syndromes Resulting From Gross Chromosomal Abnormalities, page 193

OBJ: 5