Biology Genetics Practice Test

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In an F1 generation from crossing two true-breeding parents with different traits, the offspring typically:

They show traits from both parents equally.

They show a blend of traits from both parents.

They resemble only one parent.

Dominance in Mendelian genetics explains why F1 offspring from crossing true-breeding parents with different traits typically resemble one parent in phenotype. When a true-breeding tall plant (TT) is crossed with a true-breeding short plant (tt), all offspring are tall (Tt) because the tall allele is dominant and masks the recessive one. Each F1 individual carries one tall and one short allele, but the phenotype shows only the dominant trait. You don’t get a equal mix of traits or a true blend; and although the genotype is heterozygous, the phenotype reflects the dominant characteristic rather than both traits appearing.

They are a mixture of dominant and recessive alleles in all individuals.