Help me w/ the question?

Question

Assume that in a series of experiments, plants w/ round seeds were crossed to plants w/ wrinkled seeds and the following offspring were obtained: 220 round and 180 wrinkled

a) what are the most possible genotype of each parent
b)what genotype and phenotypic ratios are expected in an F2 self-cross of a round plant

Answer 1

a)
220 is 55% of 400
180 is 45% of 400
So this is roughly half and half. Which means that the parents have to be Aa (heterozygous) and aa (homozygous recessive) :

_ A a
a Aa aa
a Aa aa

=> 50% of each phenotype. No other combination would work, try them, you'll see...

b)
If the genotype of round seed is aa, the genotype ratio of a self cross will be 100% aa and the phenotype ratio will be 100% round seed.

If the genotype of a round seed is Aa :

_ A a
A AA Aa
a Aa aa

=>genotype:
50% Aa
25% AA
25 % aa

=>phenotype
75% round seed (AA+Aa as it is dominant)
25% wrinkled seed (aa)