Steven has the dominant tongue rolling phenotype but he does not know his genotype.His wife has the recessive non-tongue rolling trait.If their son cannot roll his tongue this means ________.
A) Steven has a heterozygous genotype
B) that it is impossible to tell Steven's genotype from this information alone
C) Steven has a homozygous dominant genotype
D) Steven has a homozygous recessive genotype

Question

Quizplus · Accepted Answer

Since Steven has the dominant phenotype (tongue rolling) and his wife has the recessive phenotype (non-tongue rolling), their son's inability to roll his tongue (a recessive trait) indicates that Steven must have passed on a recessive allele. This means Steven is heterozygous (carrying one dominant and one recessive allele) for the trait.

Steven Has the Dominant Tongue Rolling Phenotype but He Does