DNA Replication Flashcards
What is necessary for life as we know it (in terms of mutation)?
low mutation rate
when are nucleotides accepted in DNA replication?
when they are correctly base paired.
where does the energy to bond more nucleotides come from?
cleaving the pyrophosphate making a monophosphate
what type of replication do we have?
semi-conservative
how did we determine the type of replication?
DNA strands are labelled with heavy nitrogen (N^15), this in the next generation still contained the N15 but also contained lighter nitrogen at N14, the next generation there is now one strand with N15 and one with N14 and the other half have both strands with N14
The DNA replication fork is ___.
asymmetrical
What are okazaki fragments?
fragments of DNA caused by the lagging strand replication
What are template strands made out of?
RNA
What does DNA primase do?
they use template DNA to synthesize short (~10nt) RNA primers
What does DNA polymerase do?
extends the RNA primer by positioning incoming deoxyribonucleoside triphosphates and incorporates them elongating the primers
when does DNA polymerase stop?
when it hits another primer
what is a sliding clamp?
this is a ring structure that goes around DNA strand to keep DNA polymerases from dissociating
what is a clamp loader?
this is how the sliding clamp gets on the DNA, it binds to the sliding clamp and using ATP it opens the rings and then the ATP will disconnect and allow the ring to close around the strand
How are the primers removed?
another DNA polymerase will come along and replace it with DNA
what is DNA ligase?
forms bonds between the two fragments (caused by the removal of the primers)
How does ligase bond fragments together?
it catalyses the re-formation of the broken phosphodiester bond using ATP
what protein unwinds DNA?
helicase
what protein relieves the stress of unwinding?
topoisomerases
What does SSB protein stand for and what do they do?
single-stranded binding protein, they stabilize and prevent re-binding
What does topoisomerase I do?
- allows for free rotation around the covalent backbone
- undoes one side of bond to be able to rotate
What does topoisomerase II do?
- aka gyrase
- cuts both strands to dientangle and pass through via a protein gate
- the gates are opened via ATP
How many replication origins do eukaryotes have?
as many as needed
How many replication origins do prokaryotes have?
one
what is DnaA? What is it found in?
initiator proteins: binds to specific sequences at replication origin and destabilization off AT rich sequences
- prokaryotes
what is DnaB? What is it found in?
Helicases, prokaryotes
what are DnaG? What is it found in?
primases, prokaryotes
DNA replication in eukaryotes must be coordinated with ___?
Mitosis
what is pol(delta)
completes Okazaki fragments on the lagging strand
what is the bacterial equivalent of pol(delta) and pol(epsilon)
DNA polymerase 3
what does pol(epsilon) do
extends the leading strand
What are telomeres and how are they added?
they are junk DNA segments at the end of Chromosomes to prevent them from shrinking after each replication, they are added via telomerases
What do T-loops do?
T-loops insert the single strand 3’ end into duplex repeats and maintain the strucutre
