Epistasis is a phenomenon in genetics in which the effect of a gene mutation is dependent on the presence or absence of mutations in one or more other genes, respectively termed modifier genes. In other words, the effect of the mutation is dependent on the genetic background in which it appears. An example of epistasis is the interaction between hair colour and baldness. A gene for total baldness would be epistatic to one for blond hair or red hair. The hair-colour genes are hypostatic to the baldness gene. The baldness phenotype supersedes genes for hair colour, and so the effects are non-additive. Various types of epistatic gene interaction are 1) Recessive epitasis (9:3:4) 2) Dominant epistasis (12:3:1) 3) Dominant and recessive (inhibitory) epistasis (13:3) 4) Duplicate recessive epistasis (9:7) 5) Duplicate dominant epistasis (15:1) and 6) Polymeric gene interaction (9:6:1).

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).