Question

In a cross between two true-breeding lineages of four-O'clock plants, there are three phenotypes (red, white, pink) in the resultant F2 hybrid offspring. (A figure is found on page 82 of your text.) At the level of visible phenotype, what is the pattern of inheritance illustrated by this cross?

Answer 1

The pattern of inheritance exhibited in the cross of four-O'clock plants is incomplete dominance, where the heterozygous offspring (pink flowers) are intermediate between the two homozygous parental phenotypes (red and white flowers).

Step-by-step explanation:

The pattern of inheritance illustrated by the cross between two true-breeding lineages of four-O'clock plants producing red, white, and pink phenotypes in the F2 hybrid offspring is incomplete dominance. Incomplete dominance occurs when the heterozygous phenotype is an intermediate between the two homozygous phenotypes. An example of this is the pink phenotype in the F2 generation resulting from crossing true-breeding red (RR) and white (rr) four-O'clock plants, leading to a 1:2:1 ratio of red:pink:white in the F2 generation. In a Punnett square analysis, this would result in the genotypes being one RR (red), two Rr (pink), and one rr (white).