Monohybrid Cross Problem Set
Problem 10: Disappearance of parental phenotypes in the F1generation
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:
||pink flower color is epistatic to red flower color.
||pink flowers are the result of a blending of the red and white genotypes.
||flower color is due to 2 or more complementary genes.
||heterozygous plants have a different phenotype than either inbred parent because of incomplete dominance of the dominant allele.
The features of crosses involving incomplete dominance are
intermediate phenotype of heterozygous individuals, and parental
phenotypes reappear in F2 when heterozygotes are crossed.
||flower color inheritance in snapdragons does not behave as a Mendelian trait.
The Biology Project
Department of Biochemistry and Molecular
University of Arizona
Thursday, October 1, 1998
Revised: November 2004
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