Two genes control one trait example

Epistasis Epistasis is when a gene at one location (locus) alters the phenotypic expression of a gene at another locus. Epistasis takes place when the action of one gene is modified by one or several other genes. These genes are sometimes called modifier genes. The gene whose phenotype is expressed is said to be epistatic, while the phenotype that is altered is said to be hypostatic. Sometimes hypostatic phenotypes are completely suppressed. Epistatic genes are not dominant over the genes they alter or suppress. Dominance refers to an interaction between alleles of the same gene, not different genes. Examples of epistasis can be seen at both the genomic level and the phenotypic level. At the genomic level, it is highly possible that under certain conditions one gene could code for a protein that prevents transcription of the other gene. At the phenotypic level, examples include the gene causing albinism hiding the gene controlling the color of a person’s hair. In another example, a gene coding for a widow’s peak would be hidden by a gene causing baldness. Epistasis is also seen in people with red hair. These individuals are homozygous for the red hair alleles, masking the expression at the brown/blonde hair loci, resulting in red hair. At least two genes are involved in hair color. One hair color phenotype (brown vs. blond) has a dominant brown allele and a recessive blond allele. A person with a brown allele will have brown hair; a person with no brown alleles will be blond. This explains why two brown-haired parents can produce a blond-haired child. The other gene pair has a non-red vs. red set of alleles, where the non-red allele is dominant and the allele for red hair is recessive. A person with two copies of the red-haired allele will have red hair, but it will be either auburn or bright reddish orange depending on whether the first gene pair gives brown or blond hair, respectively. #gene #epistasis #Allele #locus #phenotypoe #genotype