Question

In maize, a dominant allele A is necessary for seed color, as opposed to colorless (a). Another gene has a recessive allele wx that results in waxy starch, as opposed to normal starch (Wx). The two genes segregate independently. An Aa WxWx plant is test crossed. What are the phenotypes and relative frequencies of offspring?

Answer 1

• 1/2 Aa Wx wx (colored seeds, normal starch)
• 1/2 aa Wx wx (colorless seed, normal starch).

Step-by-step explanation:

• A (colored seed) is dominant over a (colorless)
• Wx (normal starch) is dominant over wx (waxy)

Both loci are independent.

A Aa WxWx individual was test crossed (crossed with a homozygous recessive aa wxwx individual).

• The homozygous recessive can only produce a wx gametes.
• The dihybrid individual can produce two types of gametes, all of them with the same frequency because the genes segregate independently: 1/2 A Wx and 1/2 a Wx

The possible offspring resulting from the combination of those gametes is:

• 1/2 Aa Wx wx (colored seeds, normal starch)
• 1/2 aa Wx wx (colorless seed, normal starch).