Question

In a species of plants, a homozygous dominant red flower (RR) is crossed with a homozygous recessive yellow flower (rr). If the F1 generation is self-crossed and the F2 generation has a phenotype ratio of red: orange: yellow of 1:2:1, which event accounts for these results?

Answer 1

Answer:

Incomplete dominance in accounting for these results.

Explanation:

Incomplete dominance is a condition where neither of the alleles completely dominates over the other one. Dominant alleles cannot completely cover up the recessive alleles. Descendents possess an intermediate phenotype between the two parental phenotypes and not the dominant one, which would appear if this would be the case of complete dominance.

In the example, a homozygous dominant red flower (RR) is crossed with a homozygous recessive yellow flower (rr), producing a new generation of 100 % heterozygote’s orange plants (Rr), an intermediate phenotype between both homozygotes.

When individuals of the first progeny interbreed, red and yellow traits appear again. In this way, the next generation is 25% homozygote red-flowered plants, 25% homozygote yellow-flowered plants, and 50% heterozygote orange-flowered plants.