Question

In a standard monohybrid cross between purple-flowered and white-flowered peas, what fraction of the purple-flowered peas in the F2 generation would you expect to be true-breeding?

(Consider only the purple-flowered F2 plants, not all of the F2 plants.)

Answer 1

1/3

Step-by-step explanation:

A standard monohybrid cross is a cross that follows the dominance/recessive pattern from Mendel's experiment.

It means the purple flower color is dominant over the white flower color.

Assuming the allele for purple flower color is P and that of the white flower color is p, a standard monohybrid cross will involve a true breeding PP and pp.

PP x pp: Pp, Pp, Pp and Pp. All the F1 offspring will have purple flowers with Pp genotype.

At F2: Pp x Pp = PP, Pp, Pp, and pp.

3/4 or 75% of the F2 offspring have purple flower color out of which 1 is true breeding for the trait.

Hence the fraction of the purple flowered peas in the F2 that is expected to be true-breeding (PP) is 1 out of 3.