Question

In a certain type of wild flower, red is the dominant color and white is the recessive color. Red flowers can be either homozygous dominant (WW) or heterozygous (Ww) in genotype. Whereas, the white flowers are always homozygous recessive (ww). For a test cross: A red flower of an unknown genotype is mated with a white flower (homozygous recessive). The following was the F1 offspring phenotypic ratio: 100% Red 0% White. What was the genotype of the unknown red flower parent?

Answer 1

Answer:

WW

Explanation:

A red flower of an unknown genotype (WW or Ww) is mated with a white flower (ww).

The white flower parent is homozygous recessive, so the only gametes it can produce have the w allele.

The F1 must have inherited the w allele from the white flower parent.

• If the red flower parent was WW, it can only produce W gametes and the F1 will be 100% heterozygous Ww with red flowers
• If the genotype were Ww, then half the F1 would be Ww with red flowers and half would be ww with white flowers.

All the F1 individuals have red flowers, so the only possibility is that the genotype of the unknown red flower parent was WW.