Ch 15 DNA Synthesis & Repair Exam 3 Flashcards
DNA Replication
- Open and unwind DNA
- Prevent opened DNA from re-sealing itself
- Synthesize an RNA primer to initiate replication
- Perform DNA replication
What way can DNA only be synthesized?
-5’ to 3’
Where does DNA replication start?
-The origin of replication
-where a bubble forms
DNA Helicase
-breaks hydrogen bonds between the base pairs at the origin
Single-Strand DNA-Binding Proteins(SSBPs)
-attach to the single stranded DNA and prevent them from snapping back together
Topoisomerase
-relieves the tension from unwinding DNA cuts, release tension, reattaches DNA ahead of replication fork
DNA Polymerase
-enzyme that makes new DNA strand
-needs a ‘landing pad’to start DNA synthesis
-works only in the 5’ to 3’ direction
-requires a 3’ end to extend from
Primase
-enzyme that synthesizes the RNA primer
-RNA polymerase-makes RNA from DNA
-does not require a primer to start synthesis
Leading Strand
-new DNA synthesized toward the replication fork
-can proceed continuously
Lagging Strand
-new DNA synthesized away from the replication fork
-cannot be made continuously
The Replisome
-the macromolecular machine that synthesized new DNA molecules
Telomeres
-ends of linear DNA molecules
-get shorter when somatic cells divide
Telomerase
-special enzyme
-hyperactive in many type of cancers
DNA Polymerase Errors
-performs base pairing
-proofreads
Mismatch Repair
-recognize the mismatch
-remove the incorrect DNA strand
-re-make DNA based off older strand
