Instructor E. Glona C: Reyusford, PhD Etam 3 24?of 124 ipn 5, 2018 Name 2. (10 p

Question

Instructor E. Glona C: Reyusford, PhD Etam 3 24?of 124 ipn 5, 2018 Name 2. (10 points) You have made a collection of mutant fruit flies that are defective in various aspects of DNA repair. You test each mutant for its hypersensitivity to three DNA-damaging agents: sunlight, nitrous acid (which causes deamination of cytosine), and formic acid (which causes depurination). The results are summarized in Figure 1, where a "yes" indicates that the mutant is more sensitive than a normal fly and blanks indicate normal sensitivity. (Please answer in detail!) sunlight nitrous acid formic acid Dracula Faust Yes Mol ve Mr Self-destruct Yes yes Yes Marguerite You Figure F.3 02 A Which mutant is most likely to be defective in the DNA repair polymerase? Why? B. What aspect of repair is most likely to be affected in the other mutants?

Explanation / Answer

A. Faust.

After deamination, base excision repair sets in to correcct the defect. The BER pathway uses DNA glycosylase that removes deaminated base creating an apurinic or apyrimidinic site which is then removed by AP endonuclease and phosphodiesterase removing the remaining nucleotide by breaking the phosphodiester bond. DNA polymerase Beta then replaces the lost nucleotide. If this DNA repair polymerase is lost as such in the Faust, it wont be able to correct the deaminated nucleotides on nitrous acid application

B. In mutants that are more sensitive to sunlight, DNA photolyase is more likely to be mutated. DNA photolyase is an enzyme that resolves the thymidine dimers formed due to UV exposure.

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