When Mendel crossed tall pea plants with short pea plants all of the offspring were tall. Which of the following explains the tall gene?
A) The tall gene is peas is recessive
C) The short gene is peas is dominant
B) The short gene in peas is recessive
D) The tall gene in peas is dominant

D: The tall gene in peas is dominant

Explanation:

When alleles are heterozygous, dominant genes will "overpower" the recessive gene.

The offspring in the pea plants had both alleles of the gene, but despite this, all of the pea plants were tall. This is because the dominant gene, the tall gene, was expressed over the recessive gene.

The correct answer is D.

B is also correct, but the question asks us to explain the tall gene, not the short one.