17. Mutation, Repair, and Recombination

What is a spontaneous mutation, and why are spontaneous mutations rare?

Describe a tautomeric shift and how it may lead to a mutation.

The family of a sixth-grade boy in Palo Alto, California, was informed by school administrators that he would have to transfer out of his middle school because they believed his mutation of the CFTR gene, which does not produce any symptoms associated with cystic fibrosis, posed a risk to other students at the school who have cystic fibrosis. After missing 11 days of school, a settlement was reached to have the boy return to school. What ethical problems might you associate with this example?

What genetic defects result in the disorder xeroderma pigmentosum (XP) in humans? How do these defects create the phenotypes associated with the disorder?

Presented here are hypothetical findings from studies of heterokaryons formed from seven human xeroderma pigmentosum cell strains:XP1 XP2 XP3 XP4 XP5 XP6 XP7XP1 -XP2 - -XP3 - - -XP4 + + + -XP5 + + + + -XP6 + + + + - -XP7 + + + + - - -Note: + = complementation; - = no complementationThese data are measurements of the occurrence or nonoccurrence of unscheduled DNA synthesis in the fused heterokaryon. None of the strains alone shows any unscheduled DNA synthesis. Which strains fall into the same complementation groups? How many different groups are revealed based on these data? What can we conclude about the genetic basis of XP from these data?