DNA Replication Flashcards
What direction is DNA replicated in?
5’ - 3’
Name as many DNA replication enzymes as you can!
there are 7
Topoisomerase DNA Helicase DNA Polymerase DNA Primase DNA Ligase Ribonuclease Repair DNA Polymerase
How is DNA Unravelled?
By Topoisomerase
Which enzyme seperates the DNA strand?
DNA Helicase
What does DNA Helicase require?
ATP to break Hydrogen Bonds
What does DNA Polymerase do?
Adds nucleotides to the 3’ end of a nucleotide chain
What does DNA Polymerase require for DNA Synthesis?
A Template strand
Oligonucleotide primer
DNA Primase
Deoxynucleotide triphosphates (dNTPs)
What is DNA replication described as?
Semi-conservative; each new strand consists of a template strand from the parental DNA and a newly synthesised strand
What is an Oligonucleotide primer?
A short strand of RNA made by DNA primase added at the beginning of synthesis and removed later.
What are dNTPs?
Deoxynucleotide triphosphates - Nucleotides with 3 phosphates attached
Where does replication of DNA begin?
The origin of replication, creating a replication fork
Describe the two strands of DNA during replication
Leading strand: Can be continuously synthesised
Lagging strand: Cannot be continuously synthesised as the 3’ end is facing away from the fork
Describe how the leading strand is synthesised
Continuously by DNA polymerase adding dNTPs to the 3’ end
Why are dNTPs used in synthesis?
Hydrolysis of the triphosphate group releases energy used to add more nucleotides
What is the synthesis of the lagging strand split up into?
Okazaki fragments
Describe the synthesis of Okazaki fragments
DNA Primase adds the Oligonucleotide primer to the template strand.
DNA Polymerase adds dNTPs at the 3’ end of the primer until the previous fragment is reached.
Describe the joining of Okazaki fragments
Ribonuclease removes the RNA primer
Repair DNA polymerase replaces the RNA with DNA
DNA ligase joins two Okazaki fragments together.
What ensures the DNA polymerase is in the right place?
The sliding clamp
What may happen during the synthesis of the lagging strand, and how is this prevented?
Local folding.
Addition of Single strand DNA binding protein.
Describe the proofreading mechanism in DNA synthesis
DNA polymerase checks the previous nucleotide is correct before adding the next.
