Chromosomal Aberrations
AGB 121 Dept. of AGB Veterinary College, Hebbal, Bangalore
Normal Structure of chromosome
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
2
Normal Karyot ype of domesti c animal s C a tt l e c h ro mo s o me s , 2 n = 6 0 , X Y. S t a i n m et h o d B rd U i n co r p o ra t i o n - A c r i d i n e O ra n g e
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
3
Karyotype of Goat
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
4
Karyotype of Sheep 54 XY & 54 XX
Ram
Ewe
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
5
Karyotype of Buffalo 50 XX and 50XY
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
6
Swine chromosomes, 2n=38,XX
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
7
Karyotype of Dog
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
8
Cat chromosomes, 2n=38, XX.
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
9
Karyotype of Horse 64 XY
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
10
Autosomal pair
Diploid (2n) Cat 38 Dog 78 Pig 38 Goat 60 Sheep 54 Cow 60 Horse 64
No. of
Sex chromosome
No. of
metacentrics acrocentric or telocentric 16 2 0 38 12 6 0 29 3 23 0 29 13 18
X M M M A A M M
Y M A M M M M A
M – Metacentric; A – Acrocentric Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
11
Chromosomal aberrations Structural 1. Translocation 2. Inversions 3.Duplication/ Additions 4. Deletions
Numerical Aneuploidy Euploidy 1. Monoploidy
2. Triploid 3. Tetraploid
1. Monosomic 2. Trisomic 3. Tetrasomic 4. Double trisomic 5. Nullosomic
i. Autotetraploid ii. Allotetraploid
4. Polyploid Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
12
Structural aberrations
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
13
Structural Aberrations • Translocation: Broken ends of two chromosomes rejoin into non-homologous portions of chromosomes. 1. Simple translocation: A piece of one chromosome goes and attaches to another chromosome. 2. Reciprocal Translocation: Involves the exchange of segments between two nonhomologous chromosomes. Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
14
Reciprocal Translocation Homozygous reciprocal translocation A
B
C
D
E
F
C
D
A
B
C
D
E
F
C
D
E
F
G
H
A
B
G
H
E
F
G
H
A
B
G
H
Both the homologous chromosome exchange parts with two homologous chromosomeDrof another pair. R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
15
•Heterozygous reciprocal translocation If only one member of each of the two homologous pair
exchange the parts. A
B
C
D
E
F
C
D
A
B
C
D
A
B
C
D
E
F
G
H
A
B
G
H
E
F
G
H
E
F
G
H
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
16
Duplication The presence of an additional chromosome segment, as compared to that normally present in a nucleus is known as Duplication. • Four types of duplication: 1. Tandem duplication 2. Reverse tandem duplication 3. Displaced duplication 4. Translocation duplication
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
17
Chromosomal Aberrations Structural abnormalities
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
18
Induced by Radiation
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
19
Chromosome conservation Studies based on : 1. Constant autosomal arm number (NAA) ranging from 30-60. 2. Chromosomal mutation- Centric fusion.
3. Similarity in the chromosome arms noticed based on various banding techniques.
Comparison of Chromosomes of Livestock • Cattle & Goat have 60 pairs and Sheep has 54 pairs. • All autosomes are acrocentric in Cattle and Goats. The X-chromosome Goat - acrocentric Cattle's -X sub-metacentric)
Y Chromosome Smaller Larger
In sheep the same differences in the sex-chromosomes are found, but in addition there are three centromere fusions of autosomes.
The chromosomes, 1/3, 2/8 and 5/11, are fused in comparison with those in cattle and goat. Therefore, the sheep has only 54 chromosomes.
Chromosomes of Buffaloes 50,XX or 50XY Based on banding the chromosome 1 to 5 in buffaloes has been formed by centric fusion of ten acrocentric autosomes of cattle: 1 and 27, 2 and 23, 8 and 19, 5 and 28 and 16 and 29, respectively.
Comparison of River and Swamp Buffalo • Riverine Buffalo-2n=50 Chromosome 4 &9 are separate. • Swamp Buffalo-2n=48 Chromosome 4 & 9 appear as enlarged pair due to chromosome translocation. • Crossbreds -2n=49 due to the 4/9 tandem fusion • F2’s may have 2n as 48,49 and 50. • Beyond 75% inheritance 2n=50
X chromosome homology Cattle- Submetacentric River Buffalo -Acrocentric
Sheep-Acrocentric with small visible ‘p’ arm Bands are conserved except that in Buffaloes the centromere is repositioned with loss of constitutive heterochromatin. Comparison of Bovine with Caprine -four chromosome transposition including centromere repositioning
Y chromosome homology Bos taurus -Submetacentric
Bos indicus -Acrocentric with small visible pericentric inversion Buffaloes-It larger than Bos taurus of because of addition of heterochromatic region
Robertsonian Translocation
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
26
Translocation
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
27
Ring chromosome
Dr R Jayashree, Asst. Prof(AGB) Veterinary College, Bangalore
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
29
Numerical Aberration
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
30
Polyploidy -Numerical abnormality
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
31
Triploidy
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
32
Monosomic
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
33
Klinefelter syndrome
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
34
Freemartin • Infertile female when born as a co-twin to a male calf • The calf will have masculanized behaviour and non functioning ovaries
Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
35
Karyotype of freemartin It is Chimeric with the sample of cells showing XX/XY chromosomes. and pigs Externally, the animal appears female, but various aspects of female reproductive development are altered due to acquisition of anti-M端llerian hormone from the male twin. It also occurs occasionally in other mammals including sheep, goats and pigs Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
36
Freemartinism
The animal originates as a female (XX), but acquires the male (XY) component in utero by exchange of some cellular material from a male twin, via vascular connections between placentas Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
37
Cri-du-chat (Cat cry syndrome): The name of the syndrome came from a cat like mewing cry from small weak infants with the disorder. Other characteristics are microcephaly (small head), broad face and saddle nose, physical and mental retardation. Cri-du-chat patients die in infancy or early childhood. The chromosome deficiency is in the short arm of chromosome 5 . Myelocytic leukemia A deletion of chromosome 22 was described by P.C.Nowell and Hungerford and was called “Philadelphia” (Ph’) chromosome after the city in which the discovery was made. Dr R Jayashree, Asst. Prof(AGB), Veterinary College, Bangalore
38