M2: DNA Replication Flashcards
3 modes of DNA replication?
Dispersive, Semi-conservative, Conservative
A pair of old and new strand of DNA
Semi-Conservative
Homologous double strand of DNA
Conservative
Double strand combined with old and new genes
Dispersive
Ratio of Semi-Conservative DNA Replication
1:3
Ratio of Conservative DNA Replication
1:3
Ratio of Dispersive DNA Replication
1:1
Proof that DNA is semi-conservative
Meselson-Stahl Experiment
DNA replication starts at a specific point called the origin of replication, and then proceeds in both directions, creating two replication forks moving away from each other
Bidirectional Synthesis
Direction of DNA replication
5’ to 3’
In bacteria, No. of replicon
In bacteria, No. of origin & No. of termination
No. of origins in yeast (bacteria)
250 - 400 origins
No. of origins in mammalian
25,000 origins
Segment of DNA that is replicated as a unit from a single origin
Replicon
Parts of replication site
Ori site and Termination site
Needed by DNA polymerase to synthesize at 5’ to 3’
Hydroxyl group at 3’
Provides energy to DNA synthesis
Cleavage of Triphosphate
Short sequences complimentary to DNA
RNA Primer
Requirements for RNA Primer
- Short RNA sequence
- Complimentary to the DNA
Kinds of Polymerase chain Reaction (PCR) Primers
DNA Primer, Forward Primer, Reverse Primer
Replicates 3’ - 5’ template
Forward Primer
Replicates 5’ - 3’ template
Reverse Primer
Enzyme replacing supercoils ahead of replisome
DNA gyrase (gyrAB)
Enzyme binding origin of replication to open double helix
Origin-binding protein (dna A)
Enzyme loading helicase at origin
Helicase loader (dnaC)
Enzyme unwinding double helix at replication fork
Helicase (dnaB)
Enzyme preventing single strands from annealing
Single-strand binding protein (ssb)
Enzyme priming new strands of DNA
Primase (dnaG)
Main polymerizing enzyme
DNA Polymerase III
Enzyme loading Pol III into sliding clamp
Clamp holder (hol A-E)
Enzyme holding Pol III on DNA
Sliding clamp (dnaN)
Enzyme stranding elongation
Polymerase subunit (dnaE)
Enzyme holding together the two core enzymes for the leading and lagging strands
Dimerization subunit (Tau) (dnaX)
Enzyme for proofreading
Proofreading subunit (dnaQ)
Enzyme excising RNA primer and fills in the gaps
DNA Polymerase I (Pol A)
Enzyme sealing nicks in DNA
DNA Ligase (lig A, lig B)