Question

Cytoplasmic male sterility is a useful tool in plant genetics because it can eliminate selfing without the need to physically remove the pollen. A corn breeder is working with multiple lines which she wants to cross to produce optimal yield. She finds one plant of the true breeding line Starlight has arisen that lacks pollen production (i.e., is male sterile). She then crosses this line with Jubilee, another true breeding line using the ovules of Starlight and pollen of Jubilee. All of the F1 are fully fertile. The F1 are selfed, and she recovers 15/16 fully fertile plants and 1/16 male sterile plants among the F2. If she takes pollen from the F1 generation and crosses it with ovules from one of the male sterile F2 plants, what offspring ratios are expected?

a) all male sterile
b) 1:1 fully fertile:male sterile

c) 3:1 fully fertile:male sterile

d) 15:1 fully fertile:male sterile

e) all fully fertile

please explain how you got the answer C! thank you

Answer 1

Because F1 generation is fully fertile so we get 3:1 fully fertile:male sterile