Replication Flashcards
why does replication need to be extremely accurate?
to preserve the integrity of the genome
what are origins?
specific regions of the DNA strand that are recognised by the initiator proteins
how is the replication semi-discontinuous?
polymerase can only add bases in the 5’ to 3’ direction so lagging strand replicated in Okazaki fragments
how does initiation begin?
initiator proteins bind to the DNA and open up the double helix
what does the PRC do?
binds to the origin and allows accessory proteins to bind
how are the components of the PRC activated?
by phosphorylation
what is the final step in initiation?
DNA polymerase are recruited
how is the leading strand replicated?
DNA polymerase epsilon binds to the RNA primer and replicates the strand
how is the lagging strand replicated?
multiple primers binds at multiple origins along the strand, polymerase delta forms the Okazaki fragments
what does RNAase do?
removes the unwanted RNA primers
what does DNA ligase do?
joins the sugar phosphate backbone back up
what prevents the reannealing of the DNA strands?
single strand binding proteins
how does termination occur?
replication complex released causing telomere extension, usually happens as a result of two replication forks colliding
what does telomerase do?
extends the telomere with repeating DNA
how does the telomerase cap form?
lots of repetitive non-coding DNA at the telomere which loops back and interacts with itself forming the sheltering complex
what is different with mitochondrial replication?
independent from nuclear DNA, uses different origin sequences to initiate replication of each DNA strand
how does mitochondrial replication begin?
H strand is used as a template for synthesis, which proceeds for a short distance
what causes the synthesis of a new strand in mitochondria?
when the displaced strand passes the origin on the L strand
