what is epistasis and differentiate between dominant and recessive epistasis??plzz help...
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Epistasis can be defined as a gene interaction whereby one gene interferes with the phenotypic expression of another non allelic gene or genes.
The gene or locus which suppresses or masks the action of a gene at another locus is called epistatic gene. The gene or locus whose expression is suppressed by an epistatic gene is called hypostatic gene.
Dominant epistasis: A dominant epistastic suppresses the expression of a non allelic gene (dominant or recessive).
F2 phenotypic ratio: 12:3:1
Example: In summer squash fruit colour may be white, yellow or green. White fruits are produced by a domain epistatic allele ‘W’. At another locus ‘Y’ for yellow fruits is dominant to its allele ‘y’ for green fruits. Dominant white hides the effect of yellow or green. A consequence of this dominant epistasis is that the hybrid ratio is modified into 12 white: 3 yellow: 1 green.
Recessive epistasis: A recessive epistastic gene suppresses the expression of a non allelic gene only when the former is in homozygous recessive state.
F2 phenotypic ratio: 9:3:4
Example: A black Labrador homozygous for the dominant alleles (BBEE) is crossed with a yellow Labrador homozygous for the recessive alleles (bbee). On intercrossing the F1, the F2 progeny was obtained in the following ratio : 9 black : 3 brown: 4 yellow.
The gene or locus which suppresses or masks the action of a gene at another locus is called epistatic gene. The gene or locus whose expression is suppressed by an epistatic gene is called hypostatic gene.
Dominant epistasis: A dominant epistastic suppresses the expression of a non allelic gene (dominant or recessive).
F2 phenotypic ratio: 12:3:1
Example: In summer squash fruit colour may be white, yellow or green. White fruits are produced by a domain epistatic allele ‘W’. At another locus ‘Y’ for yellow fruits is dominant to its allele ‘y’ for green fruits. Dominant white hides the effect of yellow or green. A consequence of this dominant epistasis is that the hybrid ratio is modified into 12 white: 3 yellow: 1 green.
Recessive epistasis: A recessive epistastic gene suppresses the expression of a non allelic gene only when the former is in homozygous recessive state.
F2 phenotypic ratio: 9:3:4
Example: A black Labrador homozygous for the dominant alleles (BBEE) is crossed with a yellow Labrador homozygous for the recessive alleles (bbee). On intercrossing the F1, the F2 progeny was obtained in the following ratio : 9 black : 3 brown: 4 yellow.
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Answer:
Explanation:phenomenon in which an allele of a gene inhibits the expression of another non allelic gene.
Difference
The condition in which recessive allele of a gene inhibits the expression of another non allelic gene.
The condition in which dominant allele of a gene inhibits the expression of another non allelic gene.
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