What is the expected ratio of tall and dwarf plants when a heterozygous tall pea plant is crossed with a dwarf plant?

Correct answer: One to one

Use T for the dominant tall allele and t for the recessive dwarf allele. The heterozygous tall parent is Tt, while the dwarf parent is tt. The first parent produces T or t gametes, and the second produces only t gametes. The offspring are Tt and tt in equal expected numbers, so the phenotype ratio is one tall to one dwarf. Hence A is correct; 3:1 applies to a heterozygote × heterozygote cross.