A recessive allele in cucumbers leads to flowers that fail t

A recessive allele in cucumbers leads to flowers that fail to open when they mature. If you perform a cross between two individuals that were both heterozygous at this locus and examined 120 of the resulting progeny, how many would you expect (on average) to have open flowers and how many would you expect to have closed flowers?

Solution

Assume that the dominant allele is A and the recessive allele is a; and the genotype of the heterozygous cucumber is, Aa. Cross between two heterozygotes will have the progeny with the following genotypes.

Aa* Aa --à AA (1/4, dominant), Aa (1/2, dominant), aa (1/4, recessive)

Means, 25% of the cucumbers are recessive. 25% of 120 is, 120/4 = 30.

Thus, total 30 cucumbers will be recessive, whose flowers fail to open when they mature.