Epistasis refers to the interaction between different genes where the effect of one gene can mask or alter the expression of another gene. This phenomenon, first described by Bateson in 1909, highlights how gene interactions can influence phenotypes beyond the typical dominant and recessive relationships. An example of epistasis is observed in the pigmentation of mice, where one coat color gene can hide the effects of another gene.

1. EPISTASIS: TYPES & EXAMPLES
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PRESENTED BY:
Dr. RAJENDRA N. CHAVHAN
DEPARTMENT OF ZOOLOGY
MAHATMA GANDHI ARTS, SCIENCE &
LATE N. P. COMMERCE COLLEGE ARMORI, DISTRICT GADCHIROLI (MS)

2. INTRODUCTION
Epistasis is a Greek word that means standing over.
Bateson used it to describe the masking effect in 1909.
Epistasis, defined generally as the interaction between different genes is a topic
of current interest in molecular and quantitative genetics.
Epistasis, is the phenomenon where the effect of one gene is dependent on the
presence of one or more genes.
An interaction between a pair of loci in which the phenotype effect of one locus depends on
the genotype at the second locus.
Genes whose phenotypes are:
Expressed Epistatic
Altered or suppressed hypostatic

3. Definition
The term epistasis describes a certain relationship between genes, where an allele of one gene (e.g., ‘spread’)
hides or masks the visible output, or phenotype, of another gene (e.g., pattern).
Epistasis is entirely different from dominant and recessive, which are terms that apply to different alleles of the
same gene (e.g., ‘bar’ is dominant to ‘barless’ and recessive to ‘check’).
Epistasis is the phenomenon of the effect of one gene (locus) being dependent on the presence of one or more
‘modifier genes’, the genetic background.
Epistasis occurs when one allele of a gene masks the expression of alleles of another gene.
The masking of the phenotypic effect of alleles at one gene by alleles of another gene.
A gene is said to be epistatic when its presence suppresses the effect of a gene at
another locus.
Epistatic genes because of their effect on (suppressed) other genes which are
described as hypostatic.

38. In epistasis, the interaction between genes is
antagonistic, such that one gene masks or interferes with
the expression of another. ... An example of epistasis is
pigmentation in mice. The wild-type coat color, agouti
(AA), is dominant to solid-colored fur (aa).