Dihybrid Cross

Problem 8: Heterozygous offspring of a dihybrid cross.

Tutorial to help answer the question

Following a SsYy x SsYy cross, what fraction of the offspring are predicted to have a genotype that is heterozygous for both characteristics?


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 heterozygous 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 heterozygous for both traits.

The Biology Project
University of Arizona
Tuesday, August 13, 1996
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