What is epistasis?

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Epistasis refers to a condition wherein different genes interact with each other with one or more genes having dominance in terms of expression while the other genes’ traits are masked or covered. Unlike standard dominant genetic types which occur within one gene, epistasis involves two different genes. The so-called dominant gene will be able to express its traits and characteristics and it is aptly referred to as the epistatic gene. The masked other gene meanwhile is called the hypostatic gene.

The study of genes considers the process of epistasis as a kind of gene mutation which is necessary for evolution. Changes are actually evident on both genes from different species and this is the reason why many scientists also refer to epistasis as a process of double mutation. One trait from one gene may become the more dominant or obvious characteristic but there are also many cases that the hypostatic gene may also present characteristics in a more subdued way. The gene for albinism for example may interact with the gene for red hair color in animals or humans. When both these genes are inherited from parents for example, many cases will exhibit only one epistatic characteristic which can either be the albinism through the very light skin color or the red color in hair. However, there may be cases that the double mutation of these genes results to both albinism and red hair. The only difference may be that the red color tends to be lighter or paler than expected.

Epistasis as a form of mutation is considered an evolutionary event for various organisms. Mutation or changes in the genes are said to be necessary in order for the organism’s biological fitness or survival. Without adapting to the environment, no interaction between genes from different species will occur and therefore stopping the process of evolution.