Chapter 12: DNA Replication Flashcards
What are the measurements for DNA double helix?
- 0.34 nm between stacked bases
- 3.4 nm per helical turn
How many bp per turn?
10
What kind of conservation is dna?
semi-conservative
Theta replication characteristic?
Bidirectional
circular dna (bacteria)
Rolling circle characteristic
Unidirectional
viruses
Linear chromosome replication characteristics?
Bidirectional
eukaryotes
What are the four things dna replication requires?
DNA pol
four dNTPs
single dna strand
RNA primer (provides 3’OH end to initiate dna synth)
Which direction is DNA synthesis?
5’->3’
How are DNA strands held together?
H-bonds
Leading strand vs lagging strand
leading strand is the same direction of unwinding and is a continuous dna strand
lagging strand is opposite to the direction of unwinding and is a non continuous dna fragments (okazaki)
What is DnaA protein?
initiator proteins that bind to oriC and cause a short stretch of dna to unwind
What is the oriC composed of?
prok - AT rich region and four DnaA binding sites
What does helicase do?
prok - binds to single stranded dna and disrupts hydrogen bonding between bp (unwinds and travels on lagging strand)
what do single-stranded binding proteins do?
prok - prevent the dna from creating hairpins
What does gyrase do?
prok - makes double stranded breaks in the dna to relieve torsional strain from unwinding
what does primase do?
prok - synthesizes short rna primer that provides 3’OH end for Dna pol to begin synthesis (primase binds to helicase)
What do Pol I and III do?
prok
Pol III - has 5’->3’ pol activity and 3’->5’ exo activity (fix mistakes)
Pol I - has 5’->3’ pol activity and 3’->5’ exo activity (fix mistakes) and 5’->3’ exo activity can remove rna primer and replace it with dna
what does ligase do?
prok - makes phosphidiester bonds between okazaki fragments
What are the 8 components of Dna synthesis in prokaryotes
DnaA (initiator protein)
helicase
single-strand binding proteins
gyrase
primase
pol III
pol I
ligase
What are the 5 unique aspects of euk replication?
- helicase binds to double stranded dna
- pol alpha - primase activity (makes primer)
- pol epsilon - performs leading strand rep
- pol delta - performs lagging strand rep
- telomeres shorten at each round of dna rep
what does telomerase do?
euk
extends 3’ end of dna eukaryotic chromosome ends (telomere problem)
what are shorter telomeres a cause of?
death and certain diseases
