[Campbell Biology P.324] In a testcross, an individual with a dominant phenotype and an unkn... | Practice Question

In a testcross, an individual with a dominant phenotype and an unknown genotype is crossed with what?

  • A: Another individual with the same dominant phenotype.
  • B: A heterozygous individual.
  • C: A homozygous individual expressing the recessive trait.
  • D: Itself (self-pollination).

Explanation

The text explicitly states: 'In a testcross, the individual with the unknown genotype is crossed with a homozygous individual expressing the recessive trait'. This is because the recessive homozygote can only contribute recessive alleles, so the resulting offspring's phenotype directly reflects the alleles contributed by the unknown parent.