replication
Terms
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copy deck
- what functions does DNA polymerase do
-
-maintains accuracy
-creates phosphodiester bond
-copies template - requirements of DNA enzymatic synthesis:
-
-4 activated precursors (dNTP's ACGT)
-Template strand
-Short primer
-Mg2+ - in the replication reaction mechanism which phosphate residue does the 3' hydroxyl attack
- ALPHA
- how is back reaction eliminated in replication
- H2O hydrolyzes PPi to 2 Pi
- Which direction does DNA polymerase move along the DNA template, and which direction is the new DNA molecule synthesized?
-
Moves along template 3'-5'
Synthesizes in 5'-3' direction - Kornberg enzyme is aka
- DNA Polymerase I
- What are the three activities of DNA polymerase I
-
DNA Polymerase
3' exonuclease
5' exonuclease - What is the function of 3' exonuclease in DNA Polymerase I
-
to remove unpaired bases added to the 3' (hydroxyl) end of growing chain.
PROOFREADS - excises incorrect base pairings. - how is the lagging strand synthesized in DNA replication
-
in okazaki fragments
short 3'-5' pieces - what enzyme synthesizes primers for DNA replication
- primase
- What enzyme elongates primers
- polymerase 3
- what kind of polymerase is PRimase
-
an RNA polymerase
actually synthesizes short RNA's as primers. -
Function of DNA polymerase 1 in dna replication:
How does it do its function? -
to remove RNA primers from the molecule.
Binds to 3' hydroxyl of okazaki fragments; sythesizes DNA while its 5' exonuclease hydrolyzes the RNA primer one nucleotide at a time. UNTIL 1 NICK is left. - what seals the last little nick in DNA during replication
- DNA ligase
- what supplies energy for DNA LIGASE to seal the last nick
- ATP or NAD hydrolysis
-
funciton of GYRASE in transcription:
-what does it require -
introduces NEGATIVE supercoils downstream of replication site to counteract gyrating from twisting as DNA unwinds.
-Requires one ATP per supercoil - What does Helicase do and how?
-
-Binds to lagging strand at fork to seperate the DNA double helix so two new strands can be synthesized.
Hydrolizes ATP for energy as leading strand advances. - WHAT DO SSB PROTEINS DO
- bind to lagging strand in wake of helicase
- How many subunits on DNA Polyerase 3?
- 17, arranged in four subassemblies.
- the names of the four subassemblies on DNA polymerase 3:
-
1. core polymerase
2. beta clamp
3. clamp loader
4. tau dimer - funciton of B-clamp
- binds to the core polymerase (site of enzyme activity) and holds it onto DNA template strand.