What is Bill's allele combination?

Name: What is Bill's allele combination?
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Question

Quizplus · Accepted Answer

Since Bill has a dominant phenotype (normal hearing), he must have at least one dominant allele (N). His parents both have the recessive phenotype (deaf), so they must be homozygous recessive (nn). Therefore, Bill's allele combination could be Nn. It cannot be NN because then he would not have inherited an n allele from either parent. It cannot be nn because he does not exhibit the recessive phenotype.

What Is Bill's Allele Combination