With the knowledge that radiation causes mutations, many assume that human-made forms of radiation are the major contributors to the mutational load in humans. What evidence suggests otherwise?

In this chapter, three features of genes or of DNA sequence that contribute to the occurrence of mutational hotspots were described. Identify those three features and briefly describe why they are associated with mutational hotspots.

Briefly compare the production of DNA double-strand breaks in bacteria versus the double-strand breaks that precede homologous recombination.

Imagine yourself as one of the team of geneticists who launches a study of the genetic effects of high-energy radiation on the surviving Japanese population immediately following the atom bomb attacks at Hiroshima and Nagasaki in 1945. Demonstrate your insights into both chromosomal and gene mutation by outlining a short-term and long-term study that addresses these radiation effects. Be sure to include strategies for considering the effects on both somatic and germ-line tissues.

During mismatch repair, why is it necessary to distinguish between the template strand and the newly made daughter strand? Describe how this is accomplished.

Marfan syndrome is an autosomal dominant disorder in humans. It results from mutation of a gene on chromosome 15 that produces the connective tissue protein fibrillin. In its wild-type form, fibrillin gives connective tissues, such as cartilage, elasticity. When mutated, however, fibrillin is rigid and produces a range of phenotypic complications, including excessive growth of the long bones of the leg and arm, sunken chest, dislocation of the lens of the eye, and susceptibility to aortic aneurysm, which can lead to sudden death in some cases.Different sets of symptoms are seen among various family members, as shown in the pedigree below. Each quadrant of the circles and squares represents a different symptom, as the key indicates.All cases of Marfan syndrome are caused by mutation of the fibrillin gene, and all family members with Marfan syndrome carry the same mutant allele. What do the differences shown in the phenotypes of family members say about the expression of the mutant allele?

Yeast are single-celled eukaryotic organisms that grow in culture as either haploids or diploids. Diploid yeast are generated when two haploid strains fuse together. Seven haploid mutant strains of yeast exhibit similar normal growth habit at 25°C, but at 37°C, they show different growth capabilities. The table below displays the growth patternResearchers induce fusion in pairs of haploid yeast strains (all possible combinations), and the resulting diploids are tested for their ability to grow at 37°C. The results of the growth experiment are shown below. How many different genes are mutated among these seven yeast strains? Identify the strains that represent each gene mutation.

Yeast are single-celled eukaryotic organisms that grow in culture as either haploids or diploids. Diploid yeast are generated when two haploid strains fuse together. Seven haploid mutant strains of yeast exhibit similar normal growth habit at 25°C, but at 37°C, they show different growth capabilities. The table below displays the growth patternHypothesize about the nature of the mutation affecting each of these mutant yeast strains, including why strains B and G display different growth habit at C37°C than the other strains.