1. DNA REPLICATION Flashcards
Can proteins recognize the base sequence of DNA without unwinding it?
Yes ex. restriction enzyme
What is DNA replication
Process of duplication of the entire genome prior to replication
What phase of the cell cycle does replication occur
S phase
What are the steps involved in DNA replication
Initiation, Elongation and Termination
Basic rules of replication
Semi-conservative starts at the 'origin' can be uni or bi directional semi-discontinuous Synthesis always in the 5-3' direction RNA primers required
What bases are broken during origin of DNA replication
A-T base pairs because it is easier to break 2 H-bonds than 3
Another name for leading strand template
left hand fork
Another name for lagging strand template
right hand fork
what enzyme does the bidirectional synthesis of the DNA double helix
DNA Polymerase
what enzyme corrects mistaken base pairings and proof reads?
DNA polymerase
what happens if a base mismatch occurs?
DNA polymerase has 3’➡️5’ exonuclease activity in order to forrest errors
Where does energy for addition of nucleotide come from
From cleavage of high energy phosphate of incoming triphosphate
Why does Dna replication have to occur in the 5’ to 3’ direction
reaction doen not proceed, as no high energy bond will be cleaved
Topoisomerase
Prevents torsion by DNA breaks
Helicases
separates 2 strands (open double helix and held it unwind)
Primase
RNA primer synthesis
Single strand binding proteins
prevent reannealing of single strands (keeps strands separated)
DNA polymerase
synthesis of new strand
Tethering protein
stabilises polymerase
DNA ligase
seals nick via phoshodiester linkage
Okazaki fragments
small fragment of new DNA
Nuclease
removes the RNA primer nucleotide by nucleotide
Repair polymerase
replaces RNA with DNA
DNA ligase
seals the sugar-phophate backbone by creating phophodiester bond (requires Mg2+ and ATP)
