What phenotypic ratio is expected in the F2 generation?
Since the F1 generation all had gray eyes and long tails, then gray is dominant to pink eyes and long is dominant to short tails. The statement “pure-breeding” means homozygous. So, if the allele for gray is P and pink is p and the allele for long is S and short is s, then the gray eyed mouse with a long tail is PPSS and the pink-eyed mouse with the short tail is ppss, so the Parental (P) cross is: gray eyes, long tails PPSS x ppss pink eyes, short tails The F1 is: PpSs, all gray eyes and long tails Cross the F1s to get an F2 generation: PpSs x PpSs Note that this is a dihybrid cross (both organisms are heterozygotes at the same two genes), so the expected phenotype ratio in the F2 is: 9 P-S-, gray eyes, long tail 3 ppS-, pink eyes, long tail 3 P-ss, gray eyes, short tail 1 ppss, pink eyes, short tail and this is approximately the ratios you see (88:27:31:10).
