DNA Replication II

Question 1

What is primase?

Answer 1

An enzyme that synthesizes short RNA sequences called primers

Question 2

When does daughter strand synthesis begin?

Answer 2

It begins when primase adds the first 10-12 nucleotides of the new strand

Question 3

What is the primer?

Answer 3

The first 10-12 nucleotides that is added by primase

Question 4

What does primase do once the primer is produced?

Answer 4

Primase detaches from the template strand
DNA pol III takes over

Question 5

What does DNA polymerase III do?

Answer 5

DNA pol III attaches to the 3’ end of the primer and adds more nucleotides to the new strand

Question 6

What are the five different DNA pols in E. coli?

Answer 6

DNA pol I
II
III
IV
V

Question 7

Which DNA pols are found in normal DNA replication?

Answer 7

DNA pol I and III

Question 8

Which DNA pols are involved in the repair and replication of damaged DNA?

Answer 8

DNA pol II, IV, and V

Question 9

What are DNA pols overall?

Answer 9

Enzymes that catalyze the formation of a phosphodiester bond between the 3’ end of a daughter strand and the phosphate group of a deoxyribonucleotide

Question 10

What occurs at the catalytic site?

Answer 10

The reaction the DNA pols adding a phosphodiester bond between the 3’ end of a daughter strand and the phosphate group of a deoxyribonucleotide

Question 11

Phosphodiester bond formation on DNA molecule (not rlly a question)

Answer 11

1. DNA pol chooses a single d_TP (insert any base)
2. DNA pol creates a phosphodiester bond between the nucleotide and the free 3’ hydroxyl group of the daughter strand
3. Two phosphate groups are removed from the d_TP
4. The nucleotide is now a d_MP once added to the new DNA strand

Question 12

What are DNA pols limited to?

Answer 12

1. DNA pol can only add nucleotides to the 3’ end of a DNA strand
2. They cannot create a phosphodiester bond between two individual nucleotides
3. They cannot add a nucleotide to the 5’ end of DNA
4. They cannot link two DNA strands together

Question 13

Why is primase necessary?

Answer 13

Primase must create the first part of the daughter strand because DNA pol III can only add nucleotides to the 3’ end of an existing strand

Question 14

What is the role of DNA pol III?

Answer 14

To extend the daughter strand by adding nucleotides to the primer in a 5’ to 3’ direction

Question 15

Why are DNA pols necessary?

Question 16

How many DNA pol III enzymes are in a replication fork?

Answer 16

Two; one for each template strand

Question 17

What direction does DNA pol III extend a primer?

Answer 17

5’ to 3’ direction

Question 18

What direction does one DNA pol III synthesize a daughter strand?

Answer 18

Daughter strand synthesis will occur in the same direction as the movement of the replication fork: AWAY from the ori

Question 19

What is the daughter strand synthesizing away from the ori called?

Answer 19

The leading strand

Question 20

What direction does the other DNA pol III move?

Answer 20

In the opposite direction of the replication fork movement: AWAY from the ori

Question 21

What is the daughter strand synthesizing toward the ori called?

Answer 21

The lagging strand

Question 22

What is continuous synthesis?

Answer 22

When the leading strand is made as one long strand extended form a single primer; no breaks

Question 23

What is discontinuous synthesis?

Answer 23

When the polymerase extends a primer in the 5’ to 3’ direction until it encounters a previous primer, detaches from the template strand, hops in the 3’ to 5’ direction along the template strand, and attaches to the next available primer. It will then extend that primer until it encounters the previous primer, at which time it will hop to the next primer.

Question 24

How are Okazaki fragments formed?

Answer 24

When polymerase detaches from the template strand, changes direction by going to the other template strand, attaches to the next available primer, and extends that primer until it reaches the previous primer and goes to the next primer (damn what)

Question 25

What is done before daughter strand synthesis is complete?

Answer 25

Primers must be removed from the daughter strands and replaced with deoxyribonucleotides

Question 26

What is the function of DNA pol I?

Answer 26

The removal of the primer ribonucleotides and their replacement with deoxyribonucleotides

Question 27

What is needed to be done once primers have been removed and replaced with DNA?

Answer 27

Okazaki fragments in the lagging strand must be linked together to create one complete daughter strand

Question 28

What is needed to link Okazaki fragments together?

Answer 28

A phosphodiester bond between the 3’ end of one Okazaki fragment and the 5’ end of the next

Question 29

What enzyme is used to connect Okazaki fragments?

Answer 29

DNA ligase

Question 30

When does termination of DNA occur?

Answer 30

When the replication folks encounter base sequences called termination (ter) sequences

Question 31

What are the two termination (ter) sequences?

Answer 31

T1 and T2

Question 32

Where are T1 and T2 located?

Answer 32

On the side of the DNA molecule opposite to oriC

Question 33

What will a protein called “termination utilization substance” (Tus) do with T1 or T2?

Answer 33

It will bind to either T1 or T2

Question 34

What will ligase do once the replication fork stops?

Answer 34

It will link the daughter strand of each new DNA molecule

Question 35

What enzyme separates the two new DNA molecules from one another?

Answer 35

Topoisomerase II