L15 - DNA replication Flashcards
(10 cards)
In what phase of the cell cycle does the cell replicate its DNA?
S
What group is at the 3’ end of the DNA, and what group does it attach to in the incoming
dNTP? What molecule is released from the reaction?
Pentose sugar, Phosphate group, pyrophosphate released
What ions are an essential part of the catalytic site in DNA polymerase, what amino acids are coordinating them, and what do the ions do?
2 Asp coordinating 2 Mg2+ ions
The ions stabilize structures and promote catalytic activity
What is exonuclease activity, and in carrying out what functions do the polymerases
use their exonuclease activity?
Removal of a nucleotide. For both, they can do 3’ to 5’ however only pol 1 can do 5’ to 3’ as it replaces the RNA primer with DNA in the lagging strand
The bacterial origin of replication has an AT‐rich region. What is the significance of this?
As A-T only has 2 H bonds, it is weaker compared to G-C, making it easier to melt and initiate replication.
Helicase has _ subunits and it is an _____
6, ATPase (using ATP to spin it to unwind DNA)
How to differentiate between leading and lagging strand?
Leading strand moves towards where helicase is, unwinding the DNA.
How many molecules of DNA polymerase III are in the replication machinery at a replication fork?
2
When a nucleotide is removed by _’ to _’ exonuclease activity because it was incorrect, can it then be added in the next correct position?
3’ to 5’
It cannot be used in another polymerisation reaction as the C that is removed isn’t CTP but dCMP as the phosphate back bone is joined and pyrophosphate is already gone, therefore it cannot be used.
What is a telomere, and what does telomerase do? What would happen if telomerase did not function in your cells? Why do prokaryotes not need telomeres?
Telomere is a structure at the end of our chromosome.
Telomerase is a ribonucleoprotein that adds the nucleotide “TTAGGG” to the 3’ end of telomeres.
If telomerase did not function, the lagging strand would get shorter and shorter. Prokaryotes don’t need telomeres because they have circular chromosomes.
