Monohybrid Cross Problem Set

Problem 9: Incomplete dominance

In Mendel's experiments, if the gene for tall (T) plants was incompletely dominant over the gene for short (t) plants, what would be the result of crossing two Tt plants?

Tutorial

A cross of two F1 hybrids, heterozygous for a single trait that displays incomplete dominance is predicted to give a 1:2:1 ratio among both the genotypes and phenotypes of the offspring. 1/4 will have the dominant phenotype (tall, TT), 1/2 will have the intermediate phenotype (Tt) resembling the parents of this cross, and 1/4 will have the recessive phenotype (short, tt.) When incomplete dominance occurs, it is not necessary to do a test cross to identify the heterozygotes.

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