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9 Cards in this Set

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DNA replication basics
-DNA replicated in Sphase, with every cell division
-must be fast and efficient
-semi-conservative-each new copy has one parent strand(template) and one daughter strand(primer)
DNA synth initiation
REPLICATION ORIGIN-initial point of duplex separation
REPLICATION FORK-point of transition b/w duplex and ssDNA, Fork advances
HELICASE PROTEIN-seperates duplex, requires E from ATP, induces pos. supercoiling ahead
SINGLE STRANDED DNA BINDING PROT.(SSB)-coats ssDNA to stabilize it
PRIMASE PROTEIN- uses (ribose)NTP's to late down short RNA primer
DNA POLYMERASE-begins adding dNTP's to 3' end of primer
DNA synth elongation
-DNA polymerase(Mg2+) adds dNTP's to 3' end
-some DNA pols have "editing" exonuclease activity(opposite thumb)-removes in reverse direction(removes nuc from 3' end)
-Right Hand-DNA lies on palm, dNTPs captured by fingers and added to primer in "synthetic site"-b/w palm and fingers, palm and thumb domain constrain duplex-avoid wrong pairing
-synthesis is Semi-Discontinuous
-done in replisome
Semi-discontinuous Synth
-Leading strand is continuously synth in 5' to 3' dirrection
-Lagging strand-discontinuous, primer is laid down and synth goes till hits 5' end of old primer-okazaki fragments
-Several RNAses cleave RNA primer
-Gap filled by DNA pol, leaving nick
-nick sealed by DNA ligase 1
processivity
-processivity=#bp synthesized/binding event, ability of pol to remain bound
-processivity is increased by Clamp Proteins-donut w/ DNA in the middle
-Eukaryotes-pol clamp=PCNA (proliferating cell nuclear antigen)
Replisome
-replisome=1)helicase,2) two pol molecules(each w/ assoc. processivity clamps),3) and a primase molec
-Helicase puls pol behind it, lagging strand releases and reassociates(controlled by clapm prot)
-ssDNA stablized by ssb when looped out b/w helicase and lagging pol
diff DNA pols
POL ALPHA/PRIMASE:
-primes synth on lagging strand by laying down RNA primer then short DNA
-not processive
-no proofreading exonuc. act.-error prone(ok, b/c RNA is removed)
POL DELTA:
-processive (assoc. w/ PCNA)
-does bulk of synth for both strands
-has editing exonuc. act.
POL EPSILON:
-processive (but w/o PCNA)
-substiture for POL DELTA
-has editing exonuc. act.
8 MORE POLS:
-primarily for DNA repair
-less processive (no PCNA)
-no editing(quick fix)
prokaryot replicon
-replicon=unit of replication (1 initiation, 1 termination
-one replicon
-seq=origin of replication
-DNA is unwound and two replisomes work in both directions-bidirectional replication.
-procedes till the replisomes meet at the terminus
eukaryot replicons and licensing
-have many replicons/chrom to speed up replication
-all must be copied once in S phase
-licensing factors controlled by cycle regulatory mechanisms
-Replication licensing steps:
1)ORC (origin recognition complex) bind to replication origin in inactive form
2)Licensing factors (cdc6,MCM) bind adj. to ORC's and activate their ability to unwind the origin and assemble replisomes (*pre-replication complex*)
3)unwinding and fork advancement results in destruction of licensing factors
4)ORC's re-assemble at origins of daughter strands (inactive) called-*post-replication complex*