Exam 18: Gene Mutation and Dna Repair

There is a spectrum of syndromes in humans known as Xeroderma pigmentosum. The individuals that have XD most commonly have mutations in their nucleotide excision DNA repair mechanisms that make them particularly susceptible to environmental mutagens such as UV light. Individuals have to be careful with how much sunlight they are exposed to since they have an extremely elevated chance for developing skin cancer.. There have been several cell lines that have been established from XD patients that can be studied in tissue culture. In an experiment several different cell lines of unknown origin were tested for their ability to undergo unscheduled DNA synthesis (UDS), an assay for DNA repair. In this assay the amount of radioactive nucleotides that are incorporated into DNA after the cell sustains a mutagenic event are measured. The amount of radioactivity incorporated is measured by the number of counts per minute (CPM). Below is a table from such an experiment. Which cell line is most likely from XD patient(s)?

Most TNRE repeats involve expansion of which codon?

In the nucleotide excision repair system, which of the following proteins is responsible for recognizing a thymine dimer to be repaired?

The mutation frequency is the ratio of the number of mutant alleles to the total number of alleles in a given population.

Photolyase in yeast is an example of what kind of DNA repair mechanism?

In the following sequence of DNA, the italicized base has been mutated. What type of mutation is this? 5' - G A T C T C C G A A T T - 3' original strand 5' - G A T C T C C C A A T T - 3' mutated strand

Which repair mechanism identifies daughter strands by methylation?

The mechanism for reactive oxygen species to cause mutation is

An example of a mutagen that integrates into the double-helix of DNA resulting in the inhibition of DNA replication would be

The complete loss of either a guanine or adenine from DNA is an example of _____.

After screening a colony of bacteria for mutations in a given gene, you discover 100 mutant colonies out of 3 million total colonies. What is the mutation frequency for this gene in the population?

Anticipation is associated with which type of mutation?

The results of the replica plating experiments by the Lederbergs supported which theory?

The wild-type eye color of Drosophila is red. A single-base mutation can occur that produces a white eye color. What statement is correct regarding this mutation?

Which repair mechanism often leads to deletions in chromosomes?