DNA Synthesis Flashcards
DNA replication is initiated at specific sites on DNA called…..
Replication origins
What is the length of Bacterial cell cycle?
20-30 minutes
How many replication origins does bacteria have?
Single replication origin on their genome
What are the phases of cell cycle in bacteria?
2 phases
S phase + M phase
What is length of mammalian cell cycle?
16-24 hours
What are phases of mammalian cell cycle?
G1, S, G2, M
G stands to Gap
S stands for synthesis
M stands for mitosis
What is purpose of G1 phase?
It allows cell to prepare for next phase
Allow synthesis of all the extra histones you need for S phase
Synthesis of DNA polymerase
Ensures building blocks for making DNA are present
What is purpose of G2 phase?
Prepare to condense chromosomes + Allow their segregation in mitosis
How many replication origins are present in eukaryotic cells?
There are multiple replication origins
What DNA polymerase are present in bacteria + what are their functions?
DNA Polymerase I = repair
DNA polymerase II = repair
DNA polymerase III = replication
Others= repair
What DNA polymerases are present in eukaryotic cells?
DNA polymerase alpha= replication DNA polymerase beta = repair DNA polymerase gamma= mitochondrion DNA polymerase delta= replication DNA polymerase epsilon = replication
What is purpose of DNA polymerase and what does it require to function?
It synthesises DNA
Acts in 5’-3’ direction
Utilises A-T and C-G base pairing to synthesise new DNA strand
Requires DNA template, DNA/RNA primer, dNTP building blocks and Mg2+ ions
What are dNTPs?
Are building blocks of DNA
There are 4 of them => dATP, dCTP, dGTP, dTTP
What is purpose of DNA helicase?
Separates base pairs producing single strands using ATP
What is purpose of topoisomerase?
Goes in front of helicase + gets rid of cells in DNA
What is purpose of primase?
Lays down some RNA so that DNA polymerase knows where to start replicating
What is purpose of DNA binding proteins?
Stabilise single stranded DNA, stop it being re-annealed with other parent strand
What is purpose of replicative DNA polymerase?
Copies parental strand
What is purpose of repair DNA polymerase?
Repair fragment + takes out RNA so it will be a full DNA strand
What is purpose of DNA ligase?
Splices fragment together
Why is error rate in DNA replication low?
Low due to base pairing + proof reading/ editing function of DNA polymerase
Mismatch repair system- corrects most of polymerase errors