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18 Cards in this Set
- Front
- Back
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survival of a cell is dependant on:
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genetic stability, which requires accurate mechanism for replication, repair of accidental lesions
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replication errors occur by ___ of bases or ____.
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mispairing or replication slippage
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transition
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subsitution of a pyrimidine with another pyrimidine or a purine with another purine
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transversion
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substitution of a pyrimidine with a purine or vice versa
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frameshifts
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due to additoin/deletion of bases
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what happens when DNA is damaged or it has mismatched bases?
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DNA will have an altered sequence during next round of replication...may lead to non-functional protein or absence of protein...need repair
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1st level of repair during replication:
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3'-5' exonuclease activity of DNA polymerase:
removes mismatched nucleotide and incorporate the correct nucleotide |
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mechanism for recogniziing mismatch in E. coli.
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both strands are methylated at A
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mechanism of recognizing mismathc in mammalian
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single strand breaks or nicks provide the repair signal....
MutS recognizes mismatched bases MutL scan the DNA for a nick |
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HNPCC
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hereditary non-polyposis colon cancer:
inherited muation in one copy of mismatch repair gene (MMR) |
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changes in DNA may occur due to:
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cellular metabolic activity
heat extreme pH radiations substances in environment |
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what are spontaneous changes, post-replication errors:
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depurination
deamination |
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UV damage can damage what?
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pyrimidine dimers
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base excision repair
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specific base is removed and repaired
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nucleotide excision repari
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a stretch of DNA strand is removed and new strand with correct base is synthesized
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Yeast repair consists of ___ genes.
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RAD
(sensitivity to RADiations) RAD3 - excision repair RAD6 - post-replication repair RAD52 - recombination-mediated repair |
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when do double strand breaks occur?
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recombination (RAG proteins)
ionizing radiation, oxidizing agents |
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Double strand breaks are repaired by:
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1. homologous end-joining (HEJ)- no sequences lost
2. non-homologous end-joining (NHEJ)-sequence loss |
