Question

A punnet square predicts a 9:3:3:1 ratio for phenotypes. Explain what that ratio means.

Answer 1

It gives the frequency with which each phenotype is observed.

It means that out of all possible outcomes (in this case, 9 + 3 + 3 + 1 = 16) outcomes, 9 members will have one phenotype, three members will have a second phenotype, three members will have a third phenotype and 1 individual will have a fourth phenotype. If we're talking about much larger groups, the relative frequencies of each phenotype will stay roughly the same.