DNA Replication

Question 1

Primase

Answer 1

Synthesises RNA primer which binds to specific DNA sequence, has an internal 3’ hydroxyl group enabling strand to be extended (type of RNA polymerase)

Question 2

DNA Polymerase III

Answer 2

Extends strand from RNA primer by adding DNA nucleotides. Knocks ssbp off as it moves, and has proof reading mechanism (exonuclease and endonuclease activity)

Question 3

Helicase

Answer 3

Unwinds DNA helix

Question 4

Topoisomerase

Answer 4

Release of tension generated by unwinding helix, cuts two strands then rejoins

Question 5

Single stranded binding proteins

Answer 5

Prevent DNA strands from snapping back together and from degrading

Question 6

DNA Polymerase I

Answer 6

Recognises RNA/DNA hybrid, removes RNA component and adds DNA nucleotide

Question 7

DNA ligase

Answer 7

Forms phosphodiester bonds (condensation of H of OH of sugar C3 and OH of phosphate group) in leading and lagging strands and between replication bubbles