Question

which term describes a type of trait that is usually expressed only when an organism has two identical alleles for the trait?

homozygous

recessive

dominant

heterozygous

Explanation:

• Homozygous: Refers to having two identical alleles (e.g., AA or aa), but it's a genotype description, not the trait expression condition.
• Recessive: A recessive trait is expressed only when the organism has two identical (homozygous) alleles for that trait (e.g., aa for a recessive trait). If there's a dominant allele (e.g., Aa), the recessive trait is masked.
• Dominant: A dominant trait is expressed even with one dominant allele (e.g., AA or Aa), so it doesn't require two identical alleles.
• Heterozygous: Has two different alleles (e.g., Aa), and dominant traits are expressed here, while recessive traits are not.

Answer:

B. recessive