Exam 1 part 2 Flashcards
Conservative replication model
one old and one brand new helix
Semiconservative replication model
one strand is parent and other is novel
Dispersive replication model
parent and new are intermixed
Initiation of replication
- replicator sequence is denatured by initiator proteins to form a replication bubble
- helicase loaded onto the DNA
- Helicase recruits primase
- primase synthesizes a short primer
Semidiscontinuous replication
- SSB proteins bind to the ssDNA in the fork
- polymermase III adds nucelotides ONLY in the 5’ to 3’ direction
- DNA gyrase relaxes the tension ahead of the replication fork
Joining of the Okazaki fragments
- Polymerase I digests RNA primer ahead of it using its 5’ to 3’ exonuclease activity and replaces it with dNTBs using its 5’ to 3’ polymerase activity
- DNA liagase seals the nick bt adjacent fragments
Polymerase III
adds dNTPs from an RNA primer in 5’ to 3’ direction
Polymerase I
digests RNA primer using 5’ to 3’ exonuclease activity
Replaces RNA primer with dNTPs using its 5’ to 3’ polyermase activity
DNA ligase
seals the nick between adjacent fragments
Primer from DNA pol I
Okazaki fragment
fidelity
accuracy of polymerase -how many mistakes
versus porcessivity
Processivity
how long polymerase can stay on the strand -how many nucleotides it can add
-if it has to correct mistake, it can’t add as many
-almost always adds the correct complimentary base pair
1/1mil is incorrect
Polymerase ____ has both 5’ to 3’ AND 3’ to 5’ exonuclease activity
Polymerase I
Replication in eukaryotes
chromosomes are linear and bigger
Many origins per chromosome
15 polymerases (many participate in repaire)
DNA is packed as it is synthesized (wrapped around histones as it comes off rep. bubble)
Replicon
unit of measurement bt bubble fusion and one origin of replication
