NEET BIOLOGY

Detailed explanation-1: -Recessive epistasis is seen in the genes that determine coat color in Labrador retrievers. These dogs may be black, brown (frequently called chocolate), or yellow; their different coat colors are determined by interactions between genes at two loci (although a number of other loci also help to determine coat color.

Detailed explanation-2: -Labradors of genotype E/-will have dark-colored fur (either black or brown) while yellow labradors have the recessive genotype e/e. Since having the genotype e/e will result in a yellow coat no matter whether the dog is B/-or b/b, carrying two copies of the e allele is recessively epistatic to the B gene.

Detailed explanation-3: -The gene that does the masking/modifying is referred to as epistatic, while the gene that is masked/modified is referred to as hypostatic. Recessive masking epistasis can be observed in the coat color of Labrador Retrievers.

Detailed explanation-4: -Labrador retriever coat color genes only come in black or chocolate. But you see yellow Labrador retrievers running around the dog park. This occurs when recessive epistatic genes called “extension genes” don’t actually allow color pigment to reach the fur.

Detailed explanation-5: -Because of epistasis, it’s rare to see those masked genes actually expressed in a dog’s coat color. One example of a “fault” allele – a gene variant that would cause a trait that is not allowed in a breed standard – is an allele that causes the brown color, which affects both hair pigment and skin pigment.