Question

Fruit color in eggplants is controlled by the amount of a particular enzyme present. Two copies of the purple allele produce enough enzyme to show the typical dark purple color in eggplants. One copy of the purple allele and one copy of the white allele results in a lighter shade called violet. Two copies of the white allele does not produce any enzyme, which results in a white eggplant. Which Punnett square represents the cross of two heterozygous plants?

Answer 1

Here, you have a case of codominance.

You know that because they tell you that in the presence of both alleles (purple and white) you have a light violet. No one is dominant over the other, both appear as a combination of alleles.

Purple: P

White W

A heterozygous plant has PW alleles.

PW x PW = PP PW WP WW

25% chances of PP (deep purple)

50% chances of PW (ligth violet)

25% chances of WW (white)