How to determine gametes from genotypes

Tutorial to help answer the question

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

Tutorial

There are four possible combinations of gametes for the AaBb parent. Half of the gametes get a dominant A and a dominant B allele; the other half of the gametes get a recessive a and a recessive b allele. Both parents produce 25% each of AB, Ab, aB, and ab. (Review problem #3's tutorial if necessary).

Page 2

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

A. 1/16

B. 1/8

C. 3/16

D. 1/4

E. 3/4

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

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