The allele of the human transport protein associated with lighter skin is found almost exclusively in people with European ancestry. The other common allele for darker skin, which appears to be the ancestral allele, is found in people with African ancestry. What is a plausible explanation for how the lighter-skin allele came to be so common in those with European ancestry?

Skin color is often one of the first traits people notice in each other. Studies in zebrafish uncovered a mutation that altered a transport protein and resulted in light-colored fish. This discovery led to the finding that the same gene in humans has a strong influence on skin pigmentation in many populations. The zebrafish mutation that reduced coloration created a null allele of the transport protein gene. Which of the following types of mutation would be most likely to create this null allele?

a. A missense mutation

b. A frameshift mutation

c. A neutral mutation

d. A silent mutation

Investigators examined the expression of transporter mRNA and protein produced in zebrafish homozygous for each of the alleles and obtained the results summarized here (+=present,−=absent). Does the allele associated with light color appear to be altering transcription ortranslation? Why?

A small portion of the human transport protein amino acid sequence is shown here. The upper sequence is associated with darker skin, and the lower sequence is associated with lighter skin. What DNA base-pair change created the light-skin form of the human protein from the gene that coded for the dark-skin form?