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.


F1 Plants
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.
F2 Plants
The F2 plants, produced by a cross of heterozygous parents, result in 3/4 of the offspring having the dominant phenotype, tall stems.

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Thursday, October 1, 1998
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