Lecture 9: DNA Replication Flashcards
Core sequence of yeast ARS1
A/TTTTAA/GTTTA/T
Mistake rate of DNA Synthesis
1 for every 10^10
How many base pairs per turn of a supercoil?
10.5 bp/turn
One RNA primer made every _____ nucleotides on the lagging strand
200
Where does ligase get its energy?
ATP hydrolyzed to AMP, then AMP is released once DNA ligase is done
What triggers release of sliding clamp loader?
It reaches the 3’ end of the primer and activates ATP hydrolysis
Basis of topoisomerase I
Cleave one DNA strand, allowing the other to rotate in controlled manner and relax the supercoil
What does topoisomerase have at its active site and where does it get energy to cleave the phosphodiester bond?
Has tyrosine, and does not need outside energy: Tyr attaches to DNA phosphate, holds it then puts it back
Where does topoisomerase II get energy?
Hydrolysis of 2 ATP
What strand does helicase travel on in prokaryotes and eukaryotes?
Lagging strand in prokaryotes, leading strand in eukaryotes
Telomere sequence
TTAGGG
How does telomerase work?
Reverse transcriptase activity: synthesizes DNA from its RNA template, which binds to overhanging 3’ end of parent template DNA
What happens to exposed 3’ strand after telomerase activity?
Folds into a T-loop, regulated by shelterin proteins - protects end of chromosome
What is replicative cell senescence?
Somatic cells with short telomeres cease dividing
What kind of cells have telomeres?
Germline cells, stem cells, some dividing somatic cells
