Question

in humans, ear wax might be controlled by a single gene showing mendelian inheritance, where the two phenotypes are wet ear wax and dry ear wax, and the wet ear wax trait is dominant to the dry ear wax trait. interested in understanding this trait, you study families and compile the following data.

	offspring with wet ear wax	offspring with dry ear wax
one parent with wet ear wax and one parent with dry ear wax	205	195
both parents with dry ear wax	0	634

what about this data suggests that ear wax is a mendelian trait governed by a single gene?
since no pairs of parents with dry ear wax produced an offspring with wet earwax, this trait is likely to be governed by a single gene.
the data do not suggest that ear wax is governed by a single trait.
there are two phenotypes and three genotypes.
there are fewer offspring with dominant alleles than with recessive alleles.

Explanation:

In Mendelian single - gene inheritance, parents with the recessive phenotype (dry ear wax here) should only pass on the recessive alleles to their offspring. So, if ear wax is a single - gene Mendelian trait, parents with dry ear wax should not produce offspring with the dominant phenotype (wet ear wax). The data shows that no pairs of parents with dry ear wax produced an offspring with wet earwax, which is consistent with single - gene Mendelian inheritance.

Answer:

Since no pairs of parents with dry ear wax produced an offspring with wet earwax, this trait is likely to be governed by a single gene.