13. Mendelian Genetics

A man has a pointed frontal hairline known as a widow's peak. This trait is thought to be controlled by a dominant allele. His wife lacks a widow's peak, and their son has a widow's peak. (W: widow's peak; w: no widow's peak). The son is curious about whether his father is homozygous or heterozygous for the widow's peak trait. Which of the following facts would allow him to know?

Tay-Sachs disease runs in Rebecca's family. On a family pedigree, she saw a shaded circle. This represented a __________.

When a trait is highly heritable,                   . a. it is influenced by genes; b. it is not influenced by the environment; c. the variance of the trait in a population can be explained primarily by variance in genotypes; d. A and C are correct; e. A, B, and C are correct