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8 Cards in this Set
- Front
- Back
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What sites are methylated in DNA?
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- Cs that precede Gs
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What is the purpose of DNA methylation?
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- regulate gene expression (inactivates a gene)
- cell differentiation - genomic imprinting - X-chromosome inactivation - DNA replication - viral latency - carcinogenesis - aging |
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What is the purpose of maintenance methylation?
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- maintains the established methylation pattern (uses paternal strand as a template to methylate the daughter strand after replication)
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What is the purposes of de novo methyltransferases?
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- add methyl groups to previously unmethylated DNA
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What causes pryimidine dimers and what are they?
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- UV radiation
- adjacent thymines covalently bond together, distorting helix and preventing proper replication |
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What are the 2 ways to correct a pyrimidine dimer? describe them
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Direct repair
- directly removes the covalent bond Excision repair - section of DNA with dimer is removed, DNA polymerase adds nucleotides, DNA ligase brings ends together |
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What happens in mismatch repair?
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- DNA polymerase incorporates an incorrect nucleotide
- usually corrects by 3' exonucleolytic actions - still isn't fixed= mismatch repair - GATC sequence is used as a template to discover which strand is the paternal - this area is brought together with the mismatch pair and all of the daughter DNA is excised out - DNA polymerase adds correct sequence |
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What mechanism causes DNA to be unstable in HNPCC (hereditary nonopolyposis colorectal cancer)?
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- microsatellite DNA: short 1/2/3 nucleotide repeats which have undergone gains/losses of these repeats which affects how accurate DNA replication is
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