TEST 3 DNA Replication Flashcards
What are the three fundamental rules of DNA replication?
Semiconservative Bidirectional Proceeds 5’ to 3’ semi-discontinuously.
What is semiconservative?
Each strand serves as a template for a new strand.
Bidirectional means what?
DNA replication is initiated at the origin of replication. Replication then spreads in both directions from these points.
What is meant by proceeds 5’ to 3’ semi discontinuously?
Synthesis is always 5’ -> 3’
Role of AAA+ ATPase
Disassociates DNA strands at origin of replication, using energy from ATP.
Role of DNA ligase
Seals nicks in the phosphodiester bonds
Role of DNA polymerase?
Hooks nucleotides together to elongate the strand.
Role of Helicase?
Present at the fork and works to unwind the fork.
Role of Endonuclease?
Cleaves the phosphodiester bonds between nucleotides inside the DNA strand.
Role of Exonuclease
Cleaves the phosphodiester bonds between nucleotides at the end of the DNA strand.
Role of Primase?
Lays down the RNA primer that DNA polymerase needs to start
Role of Topoisomerase?
Alleviates supercoiling stress.
What is required for DNA polymerase to function?
A template and a primer.
DNA poly 3 role?
Synthesizes most of the DNA
DNA poly 1 role?
Involved in DNA repair and removal of RNA primers
DNA poly 2,4,5?
Involved in DNA repair.
Steps of DNA replication?
Initiation - Melting of the DNA at origins of replication Elongation - Leading and lagging strand synthesis. Termination - halting of polymerases and resolving catenated chromosomes.
What is the only regulated phase of DNA replication?
Initiation
5’ - 3’ Polymerase activity
Synthesizes DNA
5’ - 3’ Exonuclease activity?
Removes primers
3’ - 5’ Exonuclease activity?
“Proofreading”
What are the three levels of control in DNA replication?
Geometry, Proofreading, and mismatch repair system.
Differences between Prokaryotic and Eukaryotic DNA replication?
- Eukaryotic:
- Much slower than prokaryotic
- Multiple origins of replication
- These origins are AT rich
- Telomere replication is different
- Nonmenclature is in Greek letters not roman numerals.
Polymerase alpha role?
Contains primase, initiates DNA synthesis.
Pol B role?
Repair
Poly gamma role?
Replicates mitochondrial DNA
Pol epsilon role?
Elongate the leading strand
Pol delta role?
Elongate okazaki fragments
How do eukaryotic cells protect their DNA from reacting during replication?
They are capped with Telomeres
What happens when the telomeres disappear?
Cellular Sensescence G0 state
Stops replicating.
What is cellular crisis?
Low levels of telomers, and is pushed to divide anyway.
Results in chromosomal fusion events, cancer, normally the cells die.
Where is telomerase found?
Stem cells
What is heteroplasmy?
Different cells in the body can have different mitochondrial genomes/
Where is the gene that replicates mitochondria found?
In nuclear DNA
Describe Mitochondrial depletion syndromes?
Often occur in eyes, liver, or neurons (all are high energy)
DNA that codes for mitochondrial replication is lost and thus more cannot be made.
Examples of Mitochondrial disease?
Alpers syndrome
Progressive external ophthalmoplegia
Ataxia-neuropathy syndrome.
