Exam 4

Question 1

What protein in the E. coli replication fork is 1) responsible for unwinding the DNA double helix AND 20 what is the mechanism by which this strand separation is accomplished?

Answer 1

1) helicase

2) strand separation requires ATP for energy for DNA translocation and disrupts H-bonds

Question 2

What accounts for the high fidelity of DNA polymerization?

Answer 2

Mismatches do not fit well in the active site and there is a 3’-5’ exonuclease activity that removes incorrect nucleotides at the fork

Question 3

If 15N DNA was replicated using conservative replication in 14N media through two generations, the outcome would be that there are two bands in a density gradient:

Answer 3

Both a heavy-heavy and light-light molecule bands

Question 4

Briefly describe the structure and function of the one key 1) human protein and the one key 2) E. coli protein that are each needed for high fidelity termination of DNA replication

Answer 4

1) telomerase prevents lagging strand deletion 2) Tus protein prevents fork replication past termination

Question 5

What is meant by semiconservative replication? How is this different from conservative replication?

Answer 5

Semiconservative replication creates two daughter DNA molecules