DNA Replication Flashcards
What does it mean that DNA replication is semi-conservative?
It means that each product has one preserved “parent” DNA strand and one newly synthesized strand
What does it mean that DNA replication is bidirectional?
When DNA replication begins at an origin, it moves in both directions along the helix.
What is an origin of replication, and how many are there on prokaryotes/eukaryotes?
The origin is the recognition sequence for biding proteins. They contain multiple short repeats and are AT rich. There is only one in prokaryotes, but are hundreds in Eukaryotes.
What is the replication fork?
This is the site held open by DNA helicase where H-bonds have been split to create two individual strands. At this split is where the replication machinery sits.
What is the role of Origin Binding Proteins?
Origin Binding Proteins recognize and bind to the AT streak of the origin of replication.
What is the role of Helicase in DNA replication?
Helicase breaks the H-bonds between strands and unwinds the double helix.
What is the role of single stranded binding proteins in DNA replication?
These proteins hold each single strand, keeping it from re-annealing with its complement while the DNA polymerase is working.
What is the role of the gyrase in DNA replication?
DNA gyrase is the prokaryote form of topoisomerase, and relieves extreme supercoiling by cutting and rejoining DNA in front of DNA Helicase.
What is the role of Topoisomerase?
Topoisomerase is the eukaryotic form of DNA gyrase, cutting strands and relieving supercoiling before re-annealing them.
What is the role of DNA Polymerase 1?
DNA Pol 1 is a 3 function molecule. It has a 3’-5’ and 5’-3’ exonuclease activity, and a 5’-3’ synthesis function. This does not have a sliding clamp.
What is the role of DNA Polymerase 3?
DNA Pol 3 synthesizes DNA strand and does 3’-5’ (backwards) exonuclease activity, but does not have 5’-3’ exonuclease activity. This polymerase has a sliding clamp.
What is the role of DNA Ligase?
DNA ligase is an enzyme that is responsible for sealing Okazaki fragments once the RNA primers have been replaced by pol 1.
What is the role of Telomerase?
Telomerase is the enzyme that ensures that telomeres stay at full length. They have a reverse transcriptase activity that adds more to the uniform Telomere sequence.
How are phosphodiester bonds created by DNA polymerase?
The energy of the loss of two phosphates from a dNTP to become a dNMP is coupled with the binding to the 3’ OH to create the bond.
What is the direction of synthesis of DNA?
5’-3’
