The disease, sickle-cell anemia is common in malaria-infested areas because individuals that are heterozygous for the gene (AS) have enhanced resistance to malaria over normal individuals (AA). Individuals with severe sickle-cell anemia (SS) usually die before reproduction. If this population moves to an area without malaria, what will happen to the allele frequency of the A allele over time?

The streamlined bodies seen in sharks, tuna, and dolphins best relate to

A mutation within the promoter region can alter gene transcription. Describe how this can happen.

Several species of sea urchins may inhabit the same tide pool and their reproductive periods overlap. Although they practice external fertilization, they seldom interbreed because eggs produce chemicals that are only attractive to sperm of their own species. This is an example of a ________ barrier that ________.

A mutation in the promoter region of the gene for the clotting factor IX is the cause of hemophilia B, which results in insufficient clotting. What is the likely reason for hemophilia?

Does alternative gene splicing increase or decrease the flexibility of gene expression? Explain your answer.

During development in the mother’s uterus, human embryos have pharyngeal pouches (sometimes called gill slits) that later develop into various glands. Fish also have pharyngeal pouches as embryos, but these develop into gills. The best explanation for why human and fish embryos develop pharyngeal pouches is

What would happen if RNA polymerase II did not have proofreading capabilities?

Coloration in the peppered moth (Biston betularia) is determined by a single gene with two alleles showing complete dominance. Dark moths are homozygous dominant or heterozygous for the gene, light moths are homozygous recessive. In a sample of 100 moths, you determine that 64 of the moths are dark. According to the Hardy-Weinberg rule, the expected frequency of the dominant allele is ________.

New drugs are being developed that decrease DNA methylation and prevent the removal of acetyl groups from histone proteins. Explain how these drugs could affect gene expression to help kill tumor cells.