Topic 2 Flashcards
Replicon
unit of replication between each origin
Hayflick Limit
telomeres shorten to a critical limit and cell dies
HeLa cells
bypass this limit and live indefinitely
Meselson and Stahl
Semi-conservation theory (1940s)
- put 15N DNA into a CaCl gradient with an abundance of 14N
Cairns
3H-thymidine and photographic emulsion to discover theta structure of prokaryotic circular replication
Helicase
disrupts H-bonds and unwinds DNA helix
Topoisomerase
Relaxes supercoils by causing breaks in DNA backbone
-Type 1: single-stranded breaks
-Type 2: double-stranded breaks (DNA gyrase)
SSBP
Single-stranded binding protein
- binds to unwound DNA to keep it denatured (keep from reannealing)
Primase
RNA-polymerase
-synthesizes a primer of 30bp
DNA polymerase
key synthesizing protein
1. synthesize new DNA strand from template
2. Requires primer and nucleotides
3. Synthesizes 5’->3’
4. Have 3’->5’ exonuclease activity (remove nucleotides)
5. Multi-subunit enzymes (catalytic core & holoenzymes - accessory proteins)
Ligase
seals gaps in DNA backbone
Telomerase
replicates ends of linear chromosomes (eukaryotes only)
-Includes RNA molecule, adds repeates to end of DNA w internal RNA template
Replication fork
site of replisome
Replisome
complex molecular machine
- where replication occurs (replication bubble)
Semi-discontinuous
leading strand is continuous, lagging strand is discontinuous
