DNA Replication Flashcards
Which direction to the template DNA strands run in?
3’-5’ direction
What is the name of the method of replication of the lagging strand?
Semi-discontinuous
What are the name of the discontinuously synthesized sections of DNA on the lagging strand?
Okazaki Fragments
Why is the lagging strand replicated discontinuously?
Must be synthesized in 5’-3’ direction but double helix is being unwound/unzipped in 3’-5’ direction
What is Primase?
An enzyme (type of RNA polymerase) that makes an RNA primer that signals a starting point for DNA polymerization
What is DNA polymerase III and what does it do?
Enzyme that synthesizes a new DNA strand by adding complementary nucleotides to the parental template strands.
Why can DNA polymerase III only synthesize in the 5’-3’ direction?
Only synthesizes in 5’-3’ direction because it needs an OH group to attach the phosphate group of the incoming nucleotide to
What does DNA polymerase I do?
Removes RNA primers (RNase activity )and fills gap with DNA nucleotides
What does DNA ligase do?
- Joins Okazaki fragments together ( creates phosphodiester bonds) after the RNA primers have been removes and replaced with DNA nucleotides
- joins both leading and lagging fragments from different replication bubbles togetherto make a continuous replicated strand
What does Helicase do?
Unwinds the helical double stranded DNA to give two parental templates
What enzyme is responsible for the progressive addition of new nucleotides complementary to the template strand?
DNA polymerase III
What creates a starting point for nucleotide addition?
Primase enzyme creates RNA primer
What enzyme is responsible for the release of tension generated by unwinding the DNA helix and how is it done?
Topoisomerase nicks and rejoins DNA strands
What does topoisomerase do?
releases tension build up from unwinding of helical DNA strands by nicking and rejoining DNA strands
What removes RNA primers and fills the gap with DNA nucleotides?
DNA polymerase I
