DnaA…
A binding protein
Bends DNA
Binds first 9-mer sequences
Breaks hydrogen bonds
Involved in making DNA
DnaB…
Forms helicase (enzyme)
Helicase pulls the strands further apart.
Slides alone the DNA in both directions
ATP dependent
DnaC…
carries the DnaB to 13 mer sequences.
DNA topoisomerase…
cuts one or both strands to stop tangling at one end during synthesis. (Mitigates supercoils and undoes tortional stress)
Besides cutting strands of DNA, topoisomerase also…
rejoins DNA strands.
Polymerase elongates DNA strands by…
adding nucleotides to the 3’ end of a pre-existing strand.
RNA primers are…
needed for DNA replication.
Holoenzymes are…
multi-protein complexes
DNA polymerase III…
synthesizes DNA
DNA polymerase I…
completes replication.
DNA polymerase moves ____ and removes ______.
5’ to 3’
RNA primers
DNA ligase…
seals the resulting DNA segments
A nick is…
a break in phosphodiester bonds
A gap is…
the removal of a nucleotide
The sliding clamp…
increases processivity of DNA polymerase (speed of replication).
Polymerase also….
fixes mistakes (proofreading)
Polymerase activity is…
exonuclease and removes mismatched bases.
Both (similarities) Eukaryotic and Bacterial DNA replication…
require topoisomerase + helicase
require DNA polymerase
require ligase
Eukaryotic replication… whereas Bacterial DNA don’t… (differences)
has many origins of replication
more than a dozen different DNA polymerases
DNA polymerase alpha synthesizes RNA primer ( acts as primase)
RNA primer removal is DNA by RNAase
Special case of telomere replication
Telomeres…
keep the ends of DNA from fraying. a
Are size base-pair repeat sequenes that vary in sequence and repetitions
Repeat = same six pairs over and over agains. GAA: TTT: GAA: TTT etc.
Linear DNA replication:
What is the problem with linear DNA replication?
RNA primers are left beind and removed which leaves a overhand.
Cancer can still do this
Linear DNA replication:
The priniciple that explains why cells can only duplicate so many times…
the Hayflick limit
Theories of Replication:
First Cycle: Completely new complex
Second Cycle: Multiple entirely new complex.
Conservative Replication
Theories of Replication
First Cycle: Two mixed strands
Second Cycle: Two mixed strands, two completely new strands.
Semiconservative Replication
