Chapter 9

Question 1

DNA helicases

Answer 1

unwind DNA using the energy of ATP

Question 2

What keeps the unwound single stands from internally base pairing?

Answer 2

Single strand binding proteins

Question 3

Initiator proteins

Answer 3

Opens the double strands at the origin of replication.

Called DNA A in E.coli

Question 4

What must happen to DNA before it can be replicated?

Answer 4

It must be unwound

Question 5

Where does the DNA helicases bind to to break the H bonds between the bases on the 2 strands of DNA

Answer 5

the lagging strand

Question 6

Type I (topoisomerases) (in E. coli)

Answer 6

Cuts a single strand.
Does not require DNA
Removes supercoils one at a time
Acts as axes of rotation during DNA replication

Question 7

Type II (topoisomerases) (in E. coli)

Answer 7

Cuts double strand
Requires ATP
Removes supercoils one at a time

Question 8

DNA gyrase (of E. coli)

Answer 8

topoisomerase that is essential to the unwinding process.

Breaks both strands of DNA and passes another segment of the helix through it.

Question 9

Where can DNA polymerases add a nucleotide?

Answer 9

Only to an existing 3’ hydroxyl group