DNA Repair Flashcards
A mutation in what type of cell is likely to cause cancer?
DNA repair mechanisms such that cell repair nor death is possible.
What are the three diseases associated with mutations in the Nucleotide Excision Repair mechanism?
Cockayne’s Syndrome, Xeroderma Pigmentosum, and Trichothiodystrophy.
A thymine dimerization occurs in a cell. How is this normally repaired?
Nucleotide Excision Repair
An adenine has been founded to have a bulky adduct from a known carcinogen, polycyclic aromatic hydrocarbon (PAH). What cell process would repair this DNA sequence?
Nucleotide Excision Repair
Once the Nucleotide Excision Repair mechanism is activated, what are the steps to repairing the DNA?
Cut on the phosphodiester backbone on both sides of the lesion, unwinding by DNA helicase, exonuclease destroying the single strand oligonucleotide containing the damaged nucleotide, DNA polymerase activity to replace the nucleotides, and DNA ligase comes in to seal the gap.
Glycosylases are required by what type of repair mechanism?
Base Excision Repair
Explain how glycosylase works to remove a damaged base.
Glycosylase flips the altered base out and hydrolyses the N-glycosidic bond.
A uracil is accidentally put next to an A instead of a T in DNA replication. What mechanism would repair this?
Base Excision Repair via uracil glycosylase.
Methylation of cytosine has caused problems in a DNA strand such as poor binding. What mechanism will replace this 5-methylcytosine?
Base Excision Repair via 5-methylcytosine glycosylase.
MutS and MutL proteins are used in what Mismatch repair in prokaryotes or eukaryotes?
Prokaryotes.
MSH and MLH are involved in what function in Eukaryotes?
Recognition of mismatched base pairs in the Mismatch Repair mechanism of DNA repair.
After binding of a recognition protein, how does mismatch repair proceed?
An endonuclease cleaves the phosphodiester backbone of the new DNA, an exonuclease chews this DNA up, Helicase unwinds the DNA, and DNA polymerase repairs the base pairs that are finally ligated by DNA ligase.
How is a newly synthesized strand recognized in prokaryotes?
Increased methylation of the old strand.
How is a newly synthesized strand recognized in Eukaryotes?
DNA nicks are more abundant on the old strand.
What Double Stranded DNA break repair mechanism requires sequence homology to rejoin the two broken ends?
Homologous recombination.
