Monohybrid Cross Problem Set
Problem 6: Predicting the dominant allele
When true-breeding tall stem pea plants are crossed with
true-breeding short stem pea plants, all of the ________
plants, and 3/4 of the __________ plants had tall stems.
Therefore, tall stems are dominant.
The F1 plants, produced by a cross of true-breeding (homozygous)
parents differing in a single trait, are all heterozygous and display the
dominant phenotype as shown in the Punnett square.
The F2 plants, produced by a cross of heterozygous parents, result in 3/4 of the offspring having the dominant phenotype, tall stems.
The Biology Project
Department of Biochemistry and Molecular
University of Arizona
Thursday, October 1, 1998
Revised: November 2004
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