What best describes an F1 hybrid?

• A. Offspring produced by crossing two true-breeding parents with different traits.
• B. Offspring produced by self-pollination of a single parent.
• C. Offspring that resemble both parents equally.
• D. Offspring resulting from a cross between two organisms of the same phenotype.

Answer: (A)

F1 hybrids come from crossing two true-breeding lines that differ in a trait. True-breeding means each parent is homozygous for the trait, so when they mate, all offspring in the first filial generation are genetically uniform and typically carry one allele from each parent (heterozygous). This creates the F1 generation, usually showing the dominant trait from the parents.

So this description best fits an F1 hybrid: offspring from crossing two true-breeding, contrasting parents. Self-pollinating a single parent would give the F2 generation, and crosses within the same phenotype don’t capture the contrasting parental alleles that define the F1 generation.