Question

The Yellow Agouti Conundrum

a     “black,” non-agouti, yellow hair in the ears and around the perineum

a^e    extreme non-agouti

a^t    “black-and-tan” (belly yellowish, rest of the body black)

A⁺   wild type (uniformly agouti)

A^w   “white-bellied,” or yellow-bellied agouti

A^y    “yellow,” lethal if homozygous; the heterozygote is obese

“yellow,” lethal if homozygous; the heterozygote is obese

QUESTION

A heterozygous animal AAy does not produce enough pigment and it is yellow. Homozygous individuals die during development, but AAy heterozygous do not. Why? You may use any graphic aid to explain this, if necessary (this means that you may use a Punnett square, a forking segregation diagram), or computations with fractions.

Answer 1

Answer. Heterozygous parent can produce two type of gametes i.e A and Ay so using punnett square

	A	Ay
A	AA	AAy
Ay	AAy	AyAy

So in this case homozygous AyAy will die to lethal gene while AA will be wild type and AAy will be yellow.