DNA replication Flashcards
Why does DNA replicate?
So that each cell has the full amount of DNA
What does semi-conservative replication produce?
A new DNA molecule which is half made up of the original DNA strand
What enzyme breaks the hydrogen bonds between the bases?
DNA helicase
What direction is the DNA made?
5’ to 3’
What direction is the DNA read?
3’ to 5’
What is formed after the helicase enzymes work?
A replication fork
How is a template for new DNA created?
The helix unwinding when the hydrogen bonds are broken
What are the two strands called that are formed?
Leading strand
Lagging strand
What do primase enzymes do?
They add a primer
What strand do primase enzymes add RNA nucleotides to?
Leading strand
What enzyme adds DNA nucleotides to the leading strand after the RNA nucleotides have been added?
DNA polymerase
What bond is formed when the DNA nucleotides are added?
Phosphodiester
How does the RNA have to be added onto the lagging strand?
In fragments
What are the gaps called when the RNA is added onto the lagging strand?
Okazaki fragments
What enzyme fills in the Okazaki fragments and what with?
DNA polymerase
DNA nucleotides
What enzyme removes the RNA?
exonuclease
What enzyme fills in all of the gaps to complete the lagging strand?
DNA polymerase
What enzyme binds the two strands together?
DNA ligase
Why can nucleotides only be added in a 5’ to 3’ direction? (4 marks)
1) DNA polymerase
2) Complimentary to the 3’ end of the strand
3) The active site of the enzyme only fits
4) when the DNA nucleotides are being added 5’ to 3’ direction
What is the role of DNA polymerase in DNA replication?
Adds free DNA nucleotides to the complimentary exposed bases on the template strand
