Enzymes in DNA Replication Flashcards
The 3 associated enzymatic activities of DNA polymerase I
- DNA synthesis through polymerisation of nucleotide to a free 3’ OH
- 3’-5’ exonuclease activity: NB for proofreading newly synthesised DNA to ensure if enzyme inserts an incorrect nucleotide, it can be removed & replaced
- 5’-3’ exonuclease activity: to degrade a stand ahead of the advancing polymerase such as the laid down RNA primers & in DNA repair process
What is the gene that encodes DNA polymerase I
polA gene
Studies showed a mutant E.coli isolate had a defect in polA gene but still had replication activity. What did this suggest
That there were other DNA polymerases (discovery of DNA polymerase II & III)
What are DNA polymerase I & II involved in
DNA repair
What is DNA polymerase III involved in
Bacterial DNA replication
What is the alpha subunit of eukaryotic DNA polymerase responsible for
Priming the synthesis
What is the delta subunit of eukaryotic DNA polymerase responsible for
Elongating the lagging strands
What is the epsilon subunit of eukaryotic DNA polymerase responsible for
Leading strand replication
What is the beta subunit of eukaryotic DNA polymerase responsible for
Repair
What is the gamma subunit of eukaryotic DNA polymerase responsible for
May be involved in replicating mitochondrial DNA
Function of helicases
Use energy from ATP to separate parental strands
Function of primase enzyme
- Binds to helicase to form a primosome
- Primase activated by DNA helicase
- Primase synthesises a short RNA primer approx 11 nucleotides long, to which new nucleotides can be added by DNA polymerase
Function of Topoisomerase I & DNA gyrase (a type II topoisomerase)
Wind & unwind supercoiled DNA to facilitate DNA replication
Function of single strand DNA binding protein
They bind to separated DNA strands, coat them so they cannot re-anneal
