dna replication 3 Flashcards
what will happen if the incorrect nucleotide tried to bind to the dna
there will be outer molecules called steric collutions preventing it from working even if h bonds are made
what is the error rate of pol III
10^-5
how to we decrease pol III error rate
proofreading
what does 3’-5’ exonuclease activity do and how does it work
it removes the last nucleotide added
- the pol III will stall as it recognises the last not was wrong and the end becomes an active site which cleaves the end
what are the 3 activities of pol I
- 5’-3’ polymerase synthesis
- 3’-5’ exonuclease proofreading
- 5’-3’ exonuclease nick translation
if you treat pol I with protease what are the two fragments produced and what are their functions
small n-terminal fragment 5’-3’ exocluease
large c-terminal fragment (Klenow) with polymerase and 3’-5’ exonuclease
how does nick translation work
adds nt to the nicks but also removes all the other nt and replaces them
why can rntps be directly incorporated into DNA strands
the OH on the sugar causes a steric collision
how do we remove rna from the dna within the ozkakai fragments with pol I
it will bind and use 5’-3’ exonuclease
how else can we remove rna from dna
use of rnase to remove all of the DNA other than 1
then pol 1 will remove the final rna and fill the nick
what are the fragments in the leading strand called
pseudo-okazaki fragments
what causes fragments in the leading strand
when pol III places a U nt when it should be T nt, it has to be removed
rna form instead of dna
what causes fragments in the leading strand
when pol III places a U nt when it should be T nt, it has to be removed
rna form instead of dna
what causes fragments in the leading strand
when pol III places a U nt when it should be T nt, it has to be removed
rna form instead of dna
why is u in the dna a problem
if C is deanimated, the binding of U to G will cause a mutation
how do we remove U in dna
base removed by enzyme UNG, baseless nt recognised and backbone cleaved by AP endonuclease leaves nicks behind
what seals dna nicks
dna ligase
what is the starting point for replication called for circular chromosomes and plasmids and what is it
ori
an of dsdna that is rich in A-T
in e.coli what is the replication origin point called
oriC
what does the oriC contain
three 13bp repeats and four 9bp repeats
how is the dna opened up for replication
the dnaA binds to the 9bp region and causes supercoiling and unwinding in the 13bp region (atp involved)
how is helicase loaded onto ssDNA
dnaC binds and loads it on then detaches
what happens after helicase has unwound 65nt
dna G primase will bind to it and form a primasome
what is primase and how does it work
(lots and lots of detail sorry)
it is an rna polymerase that can self prime, it does not have any editing functions
its activity is increased in the presence of helicase, so application works around replication fork
