Question

In Mendel’s crosses beginning with two pure strains of pea plants, one with yellow seeds (Y/Y) and the other with green seeds (y/y), the test cross was done between F₂ offspring with yellow seeds and a pure strain of plants with the genotype:

Options

• Y/Y

• y/y

• Y/y

• YY/yy

Answer 1

y/y

Explanation:

A test cross is used to determine whether an individual showing the dominant phenotype is homozygous dominant (Y/Y) or heterozygous (Y/y). This is done by crossing it with a homozygous recessive plant (y/y). If the F2 offspring with yellow seeds is crossed with a pure green seed (y/y) plant, the resulting progeny’s phenotype ratios can reveal the genotype of the yellow-seeded plant. Thus, the pure strain used in the test cross is y/y.