The students performed a second cross the parental cross was between Nies that are true breeding for gray bodies and long wings and flies that are true breeding for ebony bodies and curly

wings. They crossed pairs of F, fies and determined the phenotypes of the resulting F ies. The students found an approximate 3:1 ratio of this with the dominant phenotype (gray bodies

and long wings) to ties with the recessive phenotype (ebony bodies and curly wings) only a few of the flies expressed the dominant phenotype of one trait and the recessive phenotype of the

other trait.

(a) In the first analysis, all of the F, Mies from the students' crosses have the identical phenotype with respect to body color and wing shape, but the F, flies have four different phenotypes

Describe how fertilization contributes to this genetic variability.