When crossing red-fruited tomatoes (dominant trait), 87 red-fruited and 29 yellow-fruited plants

When crossing red-fruited tomatoes (dominant trait), 87 red-fruited and 29 yellow-fruited plants were obtained in the offspring. How many heterozygotes were there?

A-red-fruited

a-yellow-fruited

Since there were also yellow-fruited tomatoes in the offspring, the parents are heterozygotes (i.e., Aa and Aa). Each parent has two types of gametes (A and a). We carry out crossing.

A a A AA Aa a Aa aa
Equal ratio everywhere (i.e. 25% AA, 25% Aa, 25% Aa, 25% aa).

We know that yellow-loid is a recessive trait, which means that all 29 fruits will be homozygous (aa). We need heterozygotes (Aa), we look at the table, Aa occupies two cells, this is 50% (25% Aa + 25% Aa).

87-100%

x-50%

x = 44

Answer: 44