DNA Replication Flashcards
Replication has to be
accurate and fast
E. coli replication speed
1000 nucleotides/sec
Conservative model of replication
Parent strands are retained whole
Semi-conservative model of replication
Parent strands are paired with a complementary daughter strand
Dispersive model of replicaton
Parent and daughter strands are inter-mixed
How many bands of DNA would be expected after two rounds of conservative replication?
Two
Replication origin
The place at which replication begins (one in prokaryotes, multiple in eukaryotes)
Theta replication
circular DNA with single origin of replication that forms a replication fork and is bidirectional
Rolling circle replication
single origin of replication - new DNA spools out of the original broken circle
Eukaryotic replication
Linear replication with thousands of origins, replicons of 20,000-30,000 bp in length
Leading strand
continuous replication
Lagging strand
discontinuous replication - Okazaki fragments
Direction of replication
5’ - 3’
Initiator protein
Binds to origin and separates strands of DNA to initiate replication
Involved in: Initiation
DNA helicase
Unwinds DNA at replication fork
Involved in: Unwinding
Single strand binding proteins
Attach to single stranded DNA and prevents secondary structures from forming
Involved in: Unwinding
DNA gyrase
Moves ahead of the replication fork, making and resealing breaks in the double helical DNA to release the torque that builds up as a result of unwinding at the replication fork
Involved in: Unwinding
DNA primase
Synthesiszes a short RNA primer to provide a 3’ OH group for the attachment of DNA nucleotides
Involved in: Elongation
DNA polymerase III
Elongates a nucleotide strand from the 3’ OH group for the attachment of DNA nucleotides
Involved in: Elongation
DNA polymerase I
Removes RNA primers and replaces them with DNA
Involved in: Elongation
DNA ligase
Joins Okazaki fragments by sealing nicks in the sugar phosphate backbone of newly synthesized DNA
Involved in: Termination
Final error rate
1 in a billion
Mistake rate of DNA 5’ to 3’ polymerase
1 in 10,000 - implies proofreading activities of other polymerases
Autonomously replicating sequences
Similar to origins of replication in prokaryotes (only 100 nucleotides instead of 250)
Replication Licensing Factor
Factor that switches on the replication fork after it has been created
Telomere
End of the chromosome with a G-rich sequence
Telomerase
Riboprotein complex that adds repeated sequences, creating the telomeric region
