In pea plants, tall stem is dominant over dwarf stem. If two hybrid tall plants are crossed, what is the expected proportion of dwarf offspring?

Correct answer: One-fourth

Let T represent the dominant tall allele and t the recessive dwarf allele. A hybrid tall plant has genotype Tt, so the cross is Tt × Tt. The possible offspring are TT, Tt, Tt and tt. Only tt is dwarf, giving 1 out of 4 offspring, or 25%. Thus A is correct. The 3:1 ratio refers to tall:dwarf phenotypes, not to the dwarf proportion alone.