Question

In swine, when a pure-breeding red is crossed to a pure-breeding white, the F1 are all red. However, the F2 shows 9/16 red, 1/16 white, and 6/16 as a new color, sandy. A particular red individual (Parent 1) is crossed to a particular sandy individual (Parent 2), and the progeny is comprised of four sandy, three red, and one white piglets. What are the most likely genotypes of the two parents?

Answer 1

Answer:

Parent 1 : AaBb

Parent 2: aaBb or Aabb

Explanation:

In this cross two genes are involved and they are duplicate genes with cumulative effect i.e. individually they show the same phenotype but when together, they produce a new phenotype. Here,

A_B_ = red

aaB_ = sandy

A_bb = sandy

aabb = white

The progeny in question has a white piglet (aabb) so it must have got a set of "ab" gametes from both parents. Since parent 1 has red phenotype it should also have one A and B allele. Hence its genotype is AaBb.

Parent 2 should also contribute an "ab" pair to white piglet and it has sandy colour which is produced by either an A allele or a B allele so its genotype should be Aabb or aaBb.