Genetics 3 Flashcards
What is required of the initiation complex?
1) DnaA: recognizes origins of replication, binds AT rich regions to induce replication
2) DnaB: helicase that unwinds, creates torsional strain that is relieved by the topoisomerase
3) DnaG/primase: RNA polymerase that synthesizes primers for okazaki fragments on the lagging strand
How does DNA polymerase III works in replication
1) DnaB/helicase: main central control of DNA polymerase complex via association of topoisomerase to relieve strain
2) Cores of DNA polymerase replicate each strand simultaneously
3) Clamp loaders attach the clamps to the cores during different parts of the cycle, provides polymerase function
4) Alpha and epsilon subunits contain proofreading
Which polymerase has a 5’–>3’ exonuclease?
DNA Polymerase I
DNA Helicase
Unwinds DNA
What synthesizes the leading strand?
DNA Pol III
What synthesizes the lagging strand?
DNA Pol I: has 5’ to 3’ exonuclease activity: can remove RNA bases from the primer and replace them with DNA
Features of origin of replication
1) Rich in AT residues= easier to break apart
2) contain DNA unwinding element (DUE) made up of three sets of 13 base pairs
3) DNAA binding sequences- proteins that bind to DNA and initiate replication.
Is ATP hydrolysis requires for DNAA to initiate replication?
No.
DNAA-ATP is the active form of the protein.
Hydrolysis of ATP in this case= method for cells to regulate activity.
DNAA is inactivated when ATP is released
DNAB
DNA helicase- unwinds DNA
DNAC
Acts to deliver DNAB-helicase to newly exposed origin of replication
-ATP hydrolysis is required for interaction with DNAB.
Ter sequences
Acts as binding sites for Tus proteins
-termination requires binding of tus proteins to ter sequences to signal disassembly of replication machinery
Tus proteins
Bind DNA and signal disassembling of replication machinery.
-bind to ter sequences.
