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A Punnett square showing a typical test cross. (green pod color is dominant over yellow for pea pods [1] in contrast to pea seeds, where yellow cotyledon color is dominant over green [2]). Punnett squares for each combination of parents' colour vision status giving probabilities of their offsprings' status, each cell having 25% probability in ...
Allele frequency, or gene frequency, is the relative frequency of an allele (variant of a gene) at a particular locus in a population, expressed as a fraction or percentage. [1] Specifically, it is the fraction of all chromosomes in the population that carry that allele over the total population or sample size.
Then, p 2 is the fraction of the population homozygous for the first allele, 2pq is the fraction of heterozygotes, and q 2 is the fraction homozygous for the alternative allele. If the first allele is dominant to the second then the fraction of the population that will show the dominant phenotype is p 2 + 2 pq , and the fraction with the ...
Gene mapping or genome mapping describes the methods used to identify the location of a gene on a chromosome and the distances between genes. [2] [3] Gene mapping can also describe the distances between different sites within a gene. The essence of all genome mapping is to place a collection of molecular markers onto their respective positions ...
Genotype can also be used to refer to the alleles or variants an individual carries in a particular gene or genetic location. [2] The number of alleles an individual can have in a specific gene depends on the number of copies of each chromosome found in that species, also referred to as ploidy. In diploid species like humans, two full sets of ...
Population structure (also called genetic structure and population stratification) is the presence of a systematic difference in allele frequencies between subpopulations. In a randomly mating (or panmictic ) population, allele frequencies are expected to be roughly similar between groups.
This is the gene described in The Selfish Gene. [9] More thorough discussions of this version of a gene can be found in the articles Genetics and Gene-centered view of evolution. The molecular gene definition is more commonly used across biochemistry, molecular biology, and most of genetics—the gene that is described in terms of DNA sequence. [1]
If the genes of a gene family encode proteins, the term protein family is often used in an analogous manner to gene family. The expansion or contraction of gene families along a specific lineage can be due to chance, or can be the result of natural selection. [2] To distinguish between these two cases is often difficult in practice.