Monohybrid Cross Problem Set

Problem 10: Disappearance of parental phenotypes in the F1 generation

A genetic cross of inbred snapdragons with red flowers with inbred snapdragons with white flowers resulted in F1-hybrid offspring that all had pink flowers. When the F1 plants were self-pollinated, the resulting F2-generation plants had a phenotypic ratio of 1 red: 2 pink: 1 white. The most likely explanation is:

Tutorial

Incomplete dominance

The F1-hybrid plants have a different phenotype (pink flowers) than either of the true-breeding parents. This is an example of incomplete dominance. When the F1-hybrid plants are self-fertilized, both parental phenotypes (red flowered plants and white flowered plants) reappear in the F2 generation.

The Biology Project
Department of Biochemistry and Molecular Biophysics
University of Arizona
Thursday, October 1, 1998
Revised: November 2004
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