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Genetic variation can be identified at many levels. Identifying genetic variation is possible from observations of phenotypic variation in either quantitative traits (traits that vary continuously and are coded for by many genes, e.g., leg length in dogs) or discrete traits (traits that fall into discrete categories and are coded for by one or a few genes, e.g., white, pink, or red petal color ...
Genetic variant may refer to: Single-nucleotide polymorphism (SNP), in a case it is a common genetic variant; Mutation, in a case where it is a rare genetic variant;
In microbiology and virology, the term variant or genetic variant is used to describe a subtype of a microorganism that is genetically distinct from a main strain, but not sufficiently different to be termed a distinct strain. A similar distinction is made in botany between different cultivated varieties of a species of plant, termed cultivars.
A graphical representation of the typical human karyotype The human mitochondrial DNA. Human genetic variation is the genetic differences in and among populations.There may be multiple variants of any given gene in the human population (), a situation called polymorphism.
A rare variant is a genetic variant which occurs at low frequency in a population. [1] Rare variants play a significant role in both complex and Mendelian disease and are responsible for a portion of the missing heritability of complex diseases.
An example of a variant in an intergenic enhancer is one that is associated with blond hair color in northern Europeans. The variant in an enhancer of the KITLG gene causes only a 20% change in gene expression, yet causes hair lightening. [18] [19] An example of an intronic VUS controlling gene expression is the SNP found in an intron of the ...
Some structural variants are associated with genetic diseases, however most are not. [3] [4] Approximately 13% of the human genome is defined as structurally variant in the normal population, and there are at least 240 genes that exist as homozygous deletion polymorphisms in human populations, suggesting these genes are dispensable in humans. [4]
A null allele is a gene variant that lacks the gene's normal function because it either is not expressed, or the expressed protein is inactive. For example, at the gene locus for the ABO blood type carbohydrate antigens in humans, [13] classical genetics recognizes three alleles, I A, I B, and i, which determine compatibility of blood transfusions.