DNA structure and replication

Question 1

what is semiconservative replication?

Answer 1

each parent strand is a template, new molecules have one old and one new strand

Question 2

what are the three steps of DNA replication?

Answer 2

initiation, elongation and termination

Question 3

what happens during initiation in DNA replication?

Answer 3

• DNA helicase uses ATP start replication fork
• single strand binding proteins keeps strands from retwisting
• primase synthesizes a short RNA strand primer that binds to unzipped DNA
• DNA polymerase comes to primer site and begins elongation

Question 4

what occurs during elongation?

Answer 4

• DNA continuously opens at replication fork
• leading grows at 3’ end, Okazaki fragments form on lagging strand

Question 5

how are Okazaki fragments joined together?

Answer 5

• each fragment requires its own primer
• DNA polymerase 2 adds nucleotides to the 3’ end until it reaches the primer of the previous fragment
• DNA polymerase 1 replaces RNA primer w DNA
• DNA ligase joins Okazaki fragments together