Genome

There are different types of mutations. A point mutation is the mildest and changes just one base pair. This may or may not effectively change the structure of the protein. There can be a frameshift mutation, in which a single base is inserted or deleted. These are more serious because they can change the entire reading of the codons, causing a nonsense protein or a premature stop codon to be read that leads to a shortened, nonsensical protein. There can be large duplications, deletions, rearrangements, or inversions of big parts of the chromosome. Errors can occur when DNA is being repaired.

There can be multiple different alleles for the same trait in the population of a species. These are referred to as polymorphic genes because they can change the phenotype of the individual. The most common allele in the population is referred to as the “wild type”, while the other alleles are mutations of this allele. There is the presence of the different alleles in various frequencies because of natural selection and because of genetic drift. The wild type may not be the fittest allele and it may not be the oldest allele; it is simply the most common allele.

Some mutations do not affect anything because there are sometimes multiple codons that code for the same amino acid. These are referred to as synonymous mutations. Others will be conservative mutations because they change the amino acid but not the specific function of the protein. Mutations that are lethal or deleterious will be selectively removed from the population (through natural selection).

Some genetic diseases can be specifically due to mutations that occur in an individual or can be inherited from the individual’s parents—provided that the parents have a reasonable chance of procreating despite their mutation. A few mutations are considered beneficial to the organism, in which case it may affect the ability of the organism to thrive in the environment.

GENOME

The genome is the total amount of genetic material in an organism—including coding and non-coding segments. The size of the genome differs greatly from organism to organism. The smallest genomes are in viruses, while the largest genomes are in plants.