Question

What fraction of F₂ offspring are homozygous for both genes (pure-breeding)?

Options

• 4/16

• 1/16

• 9/16

• 1/4

Answer 1

Pure-breeding offspring (homozygous for both genes) comprise four genotypes: RRYY, RRyy, rrYY, and rryy, appearing once each in the 16 possible outcomes. This gives 4/16 or 1/4 of F₂ offspring that breed true for both traits.