Question

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

Answer 1

Answer: Option B - There are more than four genes that determine this trait.

Explanation:

The tobacco plant species have its leaf colour with characteristics that changes gradually over a range of values, which refers to continuous variation.

Note that continuous variation keep expressing gene variants in successive generations of the tobacco plants, that differs from the parents. So, there are MORE THAN four genes controling the expression of varying phenotypes in the leaves