AP BIOLOGY

Detailed explanation-1: -Autosomal single-gene Traits in Humans Single-gene autosomal traits include widow’s peak and freckles, both of which are illustrated below. Widow’s peak refers to a point in the hairline at the center of the forehead.

Detailed explanation-2: -Single-gene traits include some of the most observable physical traits in humans, like eye color, widow’s peak hairline, earlobe type (attached versus detached), presence of freckles or dimples, or the ability to roll your tongue.

Detailed explanation-3: -The genotypes WW and Ww will produce a widow’s peak (the dominant phenotype) and the ww genotype will produce no widow’s peak (the recessive phenotype). If we know the genotype of the parents, we can predict the possible genotypes and phenotypes in their offspring (first generation).

Detailed explanation-4: -If expression of a trait requires only one copy of a gene (one allele), that trait is considered dominant. If expression of a trait requires 2 copies of a gene (2 alleles), that trait is considered recessive. One exception is X-linked disorders.