Two Highly Inbred Tobacco Plants Are Crossed

Multiple Choice

Two highly inbred tobacco plants are crossed. One has dark green leaves. The other has yellow leaves. The F₁ have light green leaves. Five hundred progeny from F₁ × F₁ crosses are analyzed. Their leaves show continuous variation in color, but none has dark green or yellow leaves. What do these data suggest about the number of genes determining this trait?

A) There are two genes that determine this trait.
B) There are three genes that determine this trait.
C) There are four genes that determine this trait.
D) There are more than four genes that determine this trait.
E) There is not enough information to estimate the number of genes.