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25 Cards in this Set
- Front
- Back
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What does Helicase do?
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Separate DNA strands and unwind parental duplex
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What do topoisomerases do?
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Interconversion of DNA topoisomers
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Function of topoisomerase I
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relaxation of supercoiled DNA
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Function of topoisomerase II
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use ATP to add negative supercoils to DNA
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Does DNA polymerase require a primer?
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Yes
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Bacterial DNA Polymerase
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- DNA Pol III holoenzyme, doesn't let go of DNA until replication complete
- Much faster than DNA pol I, "Processivity" |
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Which direction does DNA replication occur?
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5' to 3'
- leading and lagging strands |
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What does DNA ligase do?
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- Formation of phosphodiester bond
- uses ATP |
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Which enzyme activity is needed for DNA pol to have proofreading function?
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- 3-5 exonuclease activity
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Eukaryotic point of origin for replication?
Prokaryotic? |
Many vs one
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Which of the eukaryotic DNA polymerase is major?
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Polymerase theta
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Players in DNA replication
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1. primase
2. helicase 3. sing-strand binding proteins 4. topoisomerase 5. DNA polymerase 6. RNase to remove primer 7. ligase |
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Name for the ends of chromosomes?
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Telomeres
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Problem of DNA replication at telomeres
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- no space for primerase to put down primer
- leads to a shorter replicated DNA |
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Solution to telomere problem
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- Telomerase adds thousands of repeated TTGGG
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When are most DNA damages dealt with?
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As soon as it is damaged
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Conditions where DNA repair pathway is inactivated?
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1. xeroderma pigmentosum
2. BRCA 3. acquired mutation |
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What does faulty DNA repair lead to?
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Mutations that will be inherited
eg. Li-Fraumini, RB, BRCA "tumor suppressor genes" |
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Term for cells with mutated DNA in tumor suppressor genes
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pre-cancerous cell
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Term for cells with more mutations, in oncogenes
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tumor cells
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Xeroderma pigmentosum
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- rare, recessive
- skin extremely sensitive to UV - will develop skin cancer easily - die from skin cancer metastases |
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HNPCC
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- Hereditary nonpolyposis colorectal cancer
- from defective DNA repair |
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General steps of DNA repair
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1. Notice DNA damage
2. Damage removal by endo/exonuclease 3. Repair DNA polymerase 4. Ligase to connect |
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Transposons
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- segments of DNA that can move to a new location
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Reverse Transcriptase
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- use single strand RNA to make DNA
- complementary DNA, "cDNA" |
