A mutation that causes a yellowing of leaves in snapdragon plants was discovered in the early 1900s. Plants with this condition, termed aurea, have less chlorophyll than green plants.

Crosses between various combinations of green and aurea plants yielded the following results.

green x green = all green
aurea x aurea = 2/3 aurea, 1/3 green
green x aurea = 1/2 green, 1/2 aurea

With respect to snapdragon color, what can be said of the G and GAalleles?

a. The GA is dominant to the G allele
b. The G^A and G alleles exhibit codominance
c. The GA allele is recessive to the G allele
d. The GA and G alleles exhibit incomplete dominance