Replication Flashcards
what is the OR and how is it different between eukaryotes and prokaryotes?
a nucleotide sequences where replication starts. it is highly conserved in prokaryotes and they only have 1. eukaryotes have many and they are variable
is prokaryotic replication bidirectional? is eukaryotic?
no. yes.
describe replication initiation
protein called DnaA binds to the OR and uses ATP to unwind the helix. DnaB (helicase) separates the DNA strands and they are held in place by single strand binding protein. a primase will create a small RNA template for DNA pol to use.
what are the beta and tau subunits of polymerase?
beta- a clamp that holds it onto the DNA strand. tau- links the polymerase from the opposing strands
what is the role of DNA Pol 1?
in lagging strands, the okazaki fragments need many primers. DNA pol3 cannot synthesize over the RNA and cannot remove them. it hops off and DNA pol1 takes over. it has the 5’-3’ exonuclease ability, so it removes the RNA primer and replaces it with DNA nts
what does topoisomerase do?
nicks DNA and puts strand “behind” nick to alleviate tension
how often does DNA Pol3 make mistakes? what are some ways they happen?
1 out of every 10^4 bases. slippage of the new strand causes insertion. slippage of the template strand causes deletion.
major differences between RNA and DNA polymerase
RNA has no exonuclease so it has a higher error rate. RNA does not require a primer
what are some differences between eukaryortes and prokaryotes?
- licensing- chromosomes only replicated once
- multiple ORs
- Chromatin folding
- Eukaryotes have mtDNA
- Eukaryotes have telomeres
mtDNA differences from chromosomes
- circular (no telomeres)
- unidirectional and uncoupled
- unlicensed
- special mtDNA Poly
what does telomerase do
adds bps to the 3’ end of the lagging strand, creating a template for which DNA poly can work off
what happens to telomeres as you age?
they shorten. thought to lead of loss of genetic information, and maybe chromosome loss and fusion
what is reverse transcriptase and what are its properties?
it makes DNA from RNA. needs a primer and template. doesnt have exonuclease capability so it is highly error prone.
in what direction does DNA replication occur? why?
5’-3’ b/c DNA Pol can only attach to 3’ ends
