Question

1. Aerobic respiration generates reactive oxygen species (ROS) that can damage guanine bases, resulting in 8-oxoguanine (8-oxo-dG) lesions, which are the major mutagenic oxidative lesions in the human genome. When DNA polymerases encounter 8-oxo-dG as a template residue, they often catalyze misincorporation of adenine instead of the “correct” cytosine pair. This results in the propagation of G to T transversions, which are common somatic mutations associated with cancer. Crystal structures of a high-fidelity DNA polymerase in the process of both accurate and mutagenic replication of 8-oxo-dG have been solved, showing how an 8-oxo-dG·dA mismatch can mimic a traditional base pair.

a) Draw a “normal” Watson-Crick base pair (including the sugar-phosphate backbone) between the nucleotides dG and dC. .

b) On the “normal” Watson-Crick base pair between dG and dC drawn above, draw in (create) the 8-oxo-dG lesion.

b) CIRCLE the nitrogen atoms at which deamination could occur.  

c) For each nucleotide, indicate the conformation around the N-glycosidic bond.

d) The Watson-Crick face of 8-oxo-dG is evident from the hydrogen bonds. Label the Hoogsteen face of 8-oxo-dG.  

e) Using the Hoogsteen face, an 8-oxo-dG(syn)·dA(anti) mismatch pair can be formed. Why do you think the mismatch pair with 8-oxo-dG in the syn conformation may be favored by the DNA polymerase enzyme?

Needing an answer/explanation for E please!

Answer 1

answer for question E)

   DNA polymerase are enzyme that build DNA in cells.DNA polymeras have the ability to check the incorrectly paired strands.This process is know as proofreading . if the enzyme finds a mismached pair it will remove and replace the neucleotide before the synthesis of DNA

   A protien complex finds a mismatched base and binds to it . another protient complex cuts the DNA near the mismatch and the enzyme cuts the icorrect nucleotide and the surrounding patch of DNA. A DNA polymerase then replaces the missing section with corrcect nucleotides and an enzyme DNA ligase seals the gap.

   HOOGSTEEN BASE PAIRING is adopted by the DNA during the replication by the ploymerase enzyme.The electron density is weak in Hoogsteen pair between a template adenine deoxyribonucleotide in the syn conformation and a deoxythymidine 5'-triphosphate , and that the fit is better for a normal Watson-Crick base pair.