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22 Cards in this Set

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  • Back
Why do different conformations in sugars occur?
Different conformations in sugars because they are enveloped not flat
What does helicase do?
seperate DNA strands
What does primase do?
supplies RNA primer for DNA polymerase
What does DNA polymerase do and in what direction?
DNA repliation, 5-3 reads 3-5
what does topoisomerase do?
relieve stress that replication produces on DNA winding
what does ligase do?
seals phosphodiester bonds
What does DNA polymerase activity require?
DNA template
Primer with free 3' OH
what is the key reaction of DNA polymerase?
nucleophilic attack by 3' OH oh pyrophosphate bond
What helps align substrates during replication?
2 Mg2+ ions in the DNA polymerase active site
What energy does DNA helicase use?
one domain hydrolyzes ATP to produce energy

second domain binds the DNA, sliding along seperating DNA
How does topoisomerase I work?
1) cutting one strand
2) allowing rotation about the remaining strand
3) reseal the break
what energy does topoisomerase use?
thermodynamically favorable, NOOOOOO ATP needed

inhibited by some cancer drugs (ex. irinotecan)
How does topoisomerase II work?
1) cuts both strands
2) passing the rest of molecule through break
3) resealing the break
What energy oes topoisomerase II use?
ATP

human version s inhibited by some cancer drugs (ex. Etoposide

bacterial versions targeted by some antibiotics
how does DNA replication begin?
RNA primer laid down by primase
During DNA replication the DNA gets smaller; how is this problem combated?
telemeres
What is the most common form of mutation?
substitution
what types of mutations cause frame shifts?
deletions and insertions
What is a synonymous mutations?
also called silent mutation, the substitution still codes for same amino acid
what are the five ways mutations can occur
1) tautomerization
2) chemical reactions
3) compounds that intercalate (slip in) between adjacent base pairs causing insertion/deletion (ex. ethidium bromide in electrophoresis)
4) detoxification enzymes can convert some compounds to mutagens
5) UV-induced linkage of adjacent pyrimidine residues in a DNA strand (THYMINE DIMER)
What are the three ways to repair DNA?
1) base excision repair
2) direct repair (ex. photochemical cleavage of pyrimidine dimers)
3) nucleotide excision repair
What are the steps of nucleotide excision repair?
1) specialized enzymes remove nucleotides adjacent to an incorrect pairing

2) the correct nucleotides are filled back in by DNA polymerase and DNA ligase acting as they always do