Question

For Mendel's pea plants, the tall phenotype is determined by a dominant allele and the dwarf phenotype is determined by a recessive allele. In the first or F1 generation, what is the outcome of a cross between true-breeding tall and true-breeding dwarf plants?

Answer 1

In Mendel's experiments, crossing true-breeding tall (TT) and dwarf (tt) pea plants results in all F1 offspring being tall (Tt), because the tall trait is determined by a dominant allele that masks the recessive dwarf allele.

Step-by-step explanation:

For Mendel's pea plants, the tall phenotype is determined by a dominant allele (T), and the dwarf phenotype is determined by a recessive allele (t). In the first generation or F1, a cross between true-breeding tall plants (TT) and true-breeding dwarf plants (tt) will result in progeny that all exhibit the tall phenotype due to the dominant allele. These offspring are heterozygous (Tt) for the trait, meaning they possess one allele for tallness and one for dwarfism, yet they display the tall phenotype because the tall allele is dominant.

Mendelian principles tell us that the appearance of the tall trait is because it's dominant, and thus it masks the expression of the recessive dwarf trait in the F1 generation. When these heterozygous plants (Tt) are crossed, Mendel discovered they follow a pattern of inheritance that produces a 3:1 ratio where the dominant phenotype (tall) is three times more likely to appear than the recessive one (dwarf) in their offspring or the F2 generation.