Question

What will be the phenotypic ratio in the offsprings obtained from the following crosses. (Note : Gene A is dominant over gene a)
(a) $Aa\times$aa (b) $AA\times aa$

Answer 1

(a) When Aa is crossed with aa

Parents: Aa x aa

Gametes: A, a and a, a

Offspring: Aa, Aa, aa, aa

So, there is 1:1 phenotypic ratio in the offsprings.

(b) When AA is crossed with aa

Parents: AA x aa

Gametes: A, A and a, a

Offspring: Aa, Aa, Aa, Aa

So, there is 1:0 phenotypic ratio in the offsprings.