DNA Replication II Flashcards
Components required for DNA synthesis
dNTPs DNA fragment template DNA polymerase Mg2+ free 3' OH
Roles and properties of DNA polymerase
phosphodiester bond
3’ OH to 5’ phosphate
Pyrophosphate released
complimentary base pairing
Acyclovir (guanine analog)
viral enzyme thymidine kinase
lack 3’ OH
Cytosine arabinoside (cytrarabine)
Vidarabine (adenosine arabinoside)
planar conformation at 3’ OH
DNA kinks
DNA polymerase III
cytosine can have tautomeric activity
3’ - 5’ proofreading exonuclease activity
Activated by improper H-bonding
Theta replication
bacterial cells
1 double stranded circle - plasmid
1 ORI (origin of replication)
Entire genomer
Rolling-Circle model - prokaryote DNA replication
Bacteriophage: viral take over
Unrolls as it replicates vs. unpeeling like a sticker in theta replication
Initial of DNA Replication (prokaryotes)
Initiator (DNAa) - breaks H-bonds, bubble formation
DNA helicase (DNAb) - primosome formation
Helicase inhibitor(DNAc) - helicase delivery/activation
DNA primase - primer
DNA polymerase I - remove primer, exonuclease, repair. (lagging strand)
DNA polymerase III - synthesis (leading strand)
SSB protein - prevent re-annealing
OriC
A-T rich
13-mer & 9-mer
DNAa binding
Initiation of replication at OriC
Initiator(DNAa) to 9-mer Strand seperation at 13mer Helicase inhibitor(DNAc) delivers helicase(DNAb) Helicase clamps ss DNA with SSB Helicase unwinds ds DNA
RNAseH and FEN-1
removes the RNA primer in eukaryotes
DNA polymerase III (prokaryotes)
okazaki fragments & leading strand
DNA polymerase I (prokaryotes)
removes RNA primer
DNA ligase
seals nicks
uses ATP
link monophosphate to 3’ OH
Follow up care to Okazaki fragments
DNA Pol I (prokaryote) or RNAseH & FEN-1 (eukaryotes) remove primer
gap filled by a DNA Pol I & III
Ligase joins
Clamp Protein
holds DNA Pol III
recognized ds DNA
triggering its release then DNA Pol III release
Supercoiling control
DNA gyrase(prokaryote) DNA topoisomerase (eukaryotes)
Ciprofloxacin
quinolone drug
inhibits bacterial DNA gyrase - allows supercoiling
URI & UTI Tx
Telomeres
repeating terminal DNA sequences
maintained by telomerase, via reverse transcriptase (RNA –> DNA)
DNA Replication:
Prokaryotes vs. Eukaryotes
1 vs. many ORI
Pol 1, 2, 3 vs alpha, beta, gama, delta
S phase vs. S-G phase
removal of primer: Pol 1 vs RNAaseH & FEN1
Prokaryotic DNA polymerases
1 - removal RNA primer, replace with DNA
3 - sun leading & lagging strand
Eukaryotic DNA Polymerases
Alpha - Syn RNA primer leading & lagging. Primes. DNA syn. Low processivity.
Delta - Syn DNA leading/lagging. High processivity. 3’-5’ proofreading.
Pol beta & gama
DNA repair
Mithochondria genome replication
Camptothecin
inhibits topoisomerase I
nicks one strand in ds DNA to fix supercoiling
Etoposide
inhibits topisomerase II
breaks both backbones to fix supercoiling
Actinomycin D (Dactinomycin)
phenoxazone ring intercalates between adjacent guanine-cytosine bases
prevents DNA replication by preventing ss DNA formation and inhibits RNA transcription(strand seperation)
