Lecture 12 - DNA Replication Flashcards
DNA/RNA run in what direction?
5’ → 3’ direction
Parental template strands run in what direction?
3’ → 5’ direction
How many chromosome pairs are there in humans?
23
What are origins of replication called?
Ori
What gives parental templates?
Unwinding of the helical double-stranded DNA
Define leading strand
Continuously synthesised in its 5’ → 3’ direction
Define lagging strand
Discontinuously synthesised in its 5’ → 3’ direction as Okazaki
fragments
What does it mean to run in a 5’ → 3’ direction?
The 5′-end (“five prime end”) designates the end of the DNA or RNA strand that has the fifth carbon in the sugar-ring of the deoxyribose or ribose at its terminus
Unwinding of the helical double-stranded DNA to give two parental templates is done by…
Helicase
Define primase
Enzyme that makes an RNA primer = starting point for DNA polymerisation
Progressive addition of new nucleotides (A, C, T or G) is done by…
DNA polymerase III
What is the role of DNA ligase?
Joins newly synthesised Okazaki fragments together (creates
phosphodiester bonds), once the RNA primers have been removed
and replaced by DNA nucleotides
How can DNA errors be repaired? (2)
Exonuclease and Endonuclease
How are exonucleases utilised?
3’to 5’ exonuclease activity of DNA pol III removes incorrect bases DURING DNA synthesis
How are endonucleases utilised?
incorrect or damaged nucleotide
bases are removed by an ENDOnuclease AFTER replication
