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The HD gene [8] is found in all human genomes. In the event that a slippage event occurs there can be a large expansion in the tandem repeats of the HD gene. [8] An individual who is not affected by Huntington's disease will have 6-35 tandem repeats at the HD locus. However, an affected individual will have 36- 121 repeats present. [7]
In contrast to a DNA damage, a mutation is an alteration of the base sequence of the DNA. Ordinarily, a mutation cannot be recognized by enzymes once the base change is present in both DNA strands, and thus a mutation is not ordinarily repaired. At the cellular level, mutations can alter protein function and regulation.
A mutation accumulation (MA) experiment is a genetic experiment in which isolated and inbred lines of organisms (so-called MA lines) are maintained such that the effect of natural selection is minimized, with the aim of quantitatively estimating the rates at which spontaneous mutations (mutations not caused by exogenous mutagens) occur in the studied organism.
Types of mutations that can be introduced by random, site-directed, combinatorial, or insertional mutagenesis. In molecular biology, mutagenesis is an important laboratory technique whereby DNA mutations are deliberately engineered to produce libraries of mutant genes, proteins, strains of bacteria, or other genetically modified organisms.
A site in a protein-coding sequence of DNA is nonsynonymous if a point mutation at that site results in a change in the amino acid, resulting in a change in the organism's phenotype. [3] Typically, silent mutations in protein-coding regions are used as the "control" in the McDonald–Kreitman test.
A hitchhiker mutation (or passenger mutation in cancer biology) may itself be neutral, advantageous, or deleterious. [ 7 ] Recombination can interrupt the process of genetic hitchhiking, ending it before the hitchhiking neutral or deleterious allele becomes fixed or goes extinct. [ 6 ]
The neutral mutation rate is affected by the amount of neutral sites in a protein or DNA sequence versus the amount of mutation in sites that are functionally constrained. By quantifying these neutral mutations in protein and/or DNA and comparing them between species or other groups of interest, rates of divergence can be determined. [33] [36]
Such duplication events are responsible for many sets of paralogous genes. [1] When an individual gene in such a set is disrupted by mutation or targeted knockout, there can be little effect on phenotype as a result of gene redundancy, whereas the effect is large for the knockout of a gene with only one copy. [2]