Dihybrid Cross

Problem 9: Homozygous offspring of a dihybrid cross, again.

Tutorial to help answer the question

In a dihybrid cross, SsYy x SsYy, what fraction of the offspring will be homozygous for both traits?


Predicting the genotype of offspring

The solution for predicting the outcome of an SsYy x SsYy genetic cross was given in detail in the tutorials for problem 2 and problem 3 . Review the answers to these problems if necessary.

These are the possible combinations of gametes for this cross.

Offspring homozygous for both traits

There are 4 out of 16 possible combinations of gametes from an SsYy x SsYy cross with the genotype of SsYy. We would therefore predict that 4/16 (or 1/4) of the offspring of the cross would be homozygous for both traits.

Note that there is a different phenotype for each of the 4 different combinations of alleles.

The Biology Project
University of Arizona
Tuesday, August 13, 1996
Contact the Development Team

All contents copyright © 1996. All rights reserved.