Question

can you guys please give me the correct answers and explain why?

3. Which of the following statements is CORRECT? A. Exposure of E.coli to UV light greatly increases the frequency of cytosine deamination B. Mutagens that intercalate into the double helix lead to the formation of thymine dimers. C) Oxidative damage to DNA usually leads to the formation of frameshift mutations. D. Some alkylating agents are mutagenic because they chemically modify amino acids in the active site of DNA polymerase III. E. A strain of E. coll carrying a mutation that inactivates the mutS gene will have a higher overall mutation frequency than a strain that carries a functional copy of this gene. 4. Base excision repair: A. Involves recognition of the damaged base by the MutS protein. B. Requires the action of an N-glycosylase to generate an abasic site. C. Requires the action of the UvrD helicase to remove a strand of DNA containing the damaged base. D. Requires primase to initiate synthesis of the repaired strand. E. Can repair the damage caused by spontaneous deamination of thymine. 5. Which of the following statements is INCORRECT? A. In bacteria, but not eukaryotes, translation begins before the mRNA is completely synthesized. B. In both eukaryotes and bacteria, the formation of the peptide bond is catalyzed by similar proteins located in the large ribosomal subunit. C. In eukaryotes, but not bacteria, the 3' end of the mRNA is believed to interact with the 5' end via contacts between poly A binding protein and the initiation factors. D. In bacteria but not eukaryotes, a mRNA may contain more than one ribosome binding site. E. In eukaryotes but not bacteria, primary transcripts of protein coding genes are extensively processed before they are translated.

Answer 1

3/ Answer :- A strain of E. coli carrying a mutation that inadirates the muts gene will have a higher overall mutation frequency than a strain that carries a functional copy of this gene. Explanation & muts gene of e.coli is involved in methy directed mismatch repair system of DNA. for this repair system the mut & encoded protein Mut-s binds to the mismatch and it is the first step of this repair system. If mutation occurs at mates and ot gets inactivated this whole repair system will fail which will increase the rate of mutation. 4 Answer: ® Requires the action of an N-glycosylase to generate an abasic site ! Explanation Po base excision repair, at first glycolyase enzyme removes the damaged base from the DNA by clearing the bound between the base and deoxyribose sugar. Thus creates an abasic site or AP site (Apwrunic on Apyrimidinic site)