Two identical alleles of the same gene are called what?

• A. Homozygous
• B. Heterozygous
• C. Dominant
• D. Recessive

Answer: (A)

Alleles for a gene come in pairs, one on each chromosome from each parent. When those two alleles are the same, the genotype is homozygous. That means you have identical genetic instructions for that gene on both inherited copies. If the two alleles were different, you’d have a heterozygous genotype.

Dominant and recessive describe how those alleles affect the trait you see (the phenotype) rather than whether the two alleles are the same, so they don’t define the term for identical alleles. For example, with a gene where one allele is for purple and the other for white, a plant with two purple alleles or two white alleles is homozygous, while a plant with one of each is heterozygous.