Ch 6 Flashcards
Semiconservative replication
Both strands can be used to replication, one old and one new strand product
Meselson and stahl experiment proved
That DNA replication is semi conservative
Enzyme that catalyzes DNA replication
DNA polymerase
Replication adds nucleotides at what carbon
3’
In replication, the cleave of triphospahte nucleotides creates
Energy to make reaction energetically favorable
Leading strand is
Continuous, no new primer needed
Lagging strand
Fragmented and together
Semi discontinuous
One strand is continuous and the other is discontinuous, continuous
4 repeated lagging strand steps
Primer synthesis, elongation, primer removal, joining of fragment
Replisome
Multiprotoen machine with a suite of basic enzymatic function
– Helicase
– Primase
– DNA polymerase
– 3’ to 5’ exonuclease.
Protein associated with replisome
Helicase, primate DNA poly, 3’ to 5’ exonuclous
DNA poly I (bacterial)
Primer removal, fills gap in fragment, involved in nucleotide excision repair pathway, turns ribose in deoxy
DNA poly I subunits and its activities
Knlenow fragmens
5’ to 3’- polymerase activity (add nucleotides)
3’ to 5’ prime exonuclease activity (fix mistakes)
2
5’ to 3’ exonuclease activity (removed primers)
DNA poly III
Main replicative polymerase,
5’ to 3’ polymerase activity
3’ to 5’ exonuclease
DNA poly II, IV, V
DNA repair mechanisms
origin of replication (OriC)
Sequence of DNA that allows for replication to begin
Bacteria origin of replication
One
E. coli initiator protien
dnaA, only binds to negativity supercoiled origin DNA
DNA helicase (dnaB) (bac)
Unwinds helix using ATP
Sliding clamps (bacteria)
tether DNA poly to the DNA
Clamp loader (bacteria)
Use ATP to open and close clamp on DNA
Single strand bind protien
Keep dna from resealing after helicase, protect nuclease attack
Primase makes
RNA primers
DNA poly III adds to dna by
Catalyzing phosodiester bond formation between nucleotides
DNA ligase
Seals up phosodiester link between fragments
Topoisomers
Same DNA, different form (linking number and mobility in gel electrophoresis)
Topoisomerase I
Caused one break in DNA, Detangle, no ATP needed
Bacterial type I topo
Relax neg supercoil
Eukaryotic type I topo
Relax negative and positive supercoiling
Type II topo
Two breaks, both positive and negatives, unknot, decatenate entangled DNA molecules, ATP needed,