What term describes individuals bred to be genetically identical at a specific locus, often true-breeding?

• A. Hybrid
• B. Homozygous
• C. F1 generation
• D. Dominant phenotype

Answer: (B)

Homozygous is the term for having two identical alleles at a single gene locus. When individuals are homozygous, they can be bred true for that locus because every gamete carries the same allele, so the offspring inherit the same genotype and phenotype for that gene across generations. True-breeding lines are typically homozygous, like AA or aa, ensuring consistent transmission of that trait. In contrast, a hybrid is heterozygous (two different alleles), so the genotype at the locus isn’t identical; the F1 generation is the first offspring from a cross and can be either homozygous or heterozygous depending on the parents; a dominant phenotype describes how a trait is expressed, not the underlying genotype.