DNA Replication I

Question 1

When does DNA replication occur?

Answer 1

When chromosomes are duplicated prior to cell division

Question 2

What happens to a single DNA molecule during DNA replication?

Answer 2

It is duplicated to create two new DNA molecules

Question 3

Is there a difference in the replicated DNA molecule and the original DNA molecule?

Answer 3

No.
The new DNA molecules are identical in base sequence to one another and to the original DNA molecule.

Question 4

What does a DNA molecule consist of?

Answer 4

Two strands with complementary base sequences

Question 5

What does semiconservative mean in replication?

Answer 5

It means the two strands are separated and the base sequence of each strand is used to create a new strand with a complementary sequence

Question 6

Whenthe two DNA molecules are created, what does each DNA molecule contain?

Answer 6

Each consists of one of the original strands and a newly synthesized complementary strand

Question 7

What does the term semiconservative mean overall?

Answer 7

It reflects the fact that one original strand is conserved in each new DNA molecule, but that the second strand is new

Question 8

What are the base sequences of the original strands used for in replication?

Answer 8

They are used to create new complementary strands

Question 9

What is the original strand called in replication?

Answer 9

Template strand
Parental strand

Question 10

What are the new strands called during replication?

Answer 10

Daughter strands

Question 11

At the end of replication, what does the replicated DNA molecule contain?

Answer 11

There are two DNA molecules, each containing one template and one daughter strand

Question 12

What is the shape of DNA in E. coli?

Answer 12

Circular

Question 13

What kind of orientation does DNA have in E. Coli?

Answer 13

Antiparallel orientation

Question 14

What is the first step in DNA replication?

Answer 14

To create an area within the DNA molecule where the two template strands are separated

Question 15

Where does strand separation begin?

Answer 15

At a specific site within the DNA molecule called the origin of replication (ori)

Question 16

What is oriC?

Answer 16

The ori in coli

Question 17

What does oriC contain?

Answer 17

Specific base sequences that are important for the initiation of replication

Question 18

What are the three types of base sequences in oriC?

Answer 18

A—T rush region
DnaA boxes
GATC methylation sites

Question 19

When does initiation start?

Answer 19

When DnaA proteins bind to DnaA boxes within oriC

Question 20

What happens when DnaA proteins are bound to DnaA boxes?

Answer 20

DnaA protein interact with one another to form a complex

Question 21

How many H bonds are in A—T? What does that mean?

Answer 21

There are two H bonds in between adenine and thymine.
This means it is easier to break the base pairs when compared to G—C, which have three H bonds

Question 22

What do the GATC methylation sites do?

Answer 22

They prevent premature initiation of a second round of DNA replication

Question 23

What happens once the two DNA strands are separated at the AT rich regions?

Answer 23

DnaA proteins recruit DNA helicases to the separated regions

Question 24

How many DNA helicase proteins are on each template strand?

Answer 24

Each template strand is bound by one DNA helicase

Question 25

What direction does DNA helicase move?

Answer 25

5’ to 3’ direction

Question 26

What does DNA helicase do as it moves down the template strand?

Answer 26

It breaks the H bonds that hold the template strands together, separating the strands, and uncoiling the DNA helix

Question 27

Do the DNA helicase proteins move in the same direction at the same time?

Answer 27

No, they move in opposite direction away from the ori. This is because DNA strands are antiparallel

Question 28

What do single-strand binding proteins prevent template strands from doing?

Answer 28

They attach to the separated template strands to prevent them from coming back together and reforming those bonds between bases.

This is because the bases within the two template strands have a natural tendency to reform H bonds.

Question 29

What does the separation of the template strands allow for?

Answer 29

It allows for daughter strand synthesis to begin

Question 30

What is a replication fork?

Answer 30

An area where the template strands are separated and where daughter strand synthesis is occurring

Question 31

Why are there always two replication forks?

Answer 31

This is because separation and unwinding of the template strands occurs bidirectionally

Question 32

What happens to the position of replication forks over time?

Answer 32

The positions will change, continuously moving farther and farther away from oriC