DNA Replication

Question 1

What type of replication does DNA undergo?

Answer 1

Semi-conservative.

Question 2

What is each DNA strand composed of during replication?

Answer 2

One existing (parent) half and one newly synthesized (daughter) half.

Question 3

Who confirmed the semi-conservative replication model and in what year?

Answer 3

Meselson and Stahl, 1957.

Question 4

What binds to specific sites on the DNA to start replication?

Answer 4

Proteins.

Question 5

What enzyme unwinds the double helix?

Answer 5

DNA helicase.

Question 6

What prevents DNA strands from reannealing during replication?

Answer 6

Single-Stranded Binding Proteins (SSBs).

Question 7

What enzyme relieves tension in the DNA strands?

Answer 7

DNA gyrase and topoisomerase.

Question 8

What is the role of DNA Polymerase III?

Answer 8

Builds the complementary strand by adding free DNTP

Question 9

In which direction does DNA Polymerase III synthesize DNA?

Answer 9

5’ to 3’.

Question 10

What provides the starting point for DNA Polymerase III?

Answer 10

An RNA primer inserted by a primase enzyme.

Question 11

What type of energy drives the addition of nucleotides?

Answer 11

Energy from the breaking of phosphate bonds.

Question 12

What is the leading strand?

Answer 12

The strand synthesized continuously in the 5’ to 3’ direction.

Question 13

What is the lagging strand?

Answer 13

The strand synthesized discontinuously in short Okazaki fragments.

Question 14

What joins Okazaki fragments together?

Answer 14

DNA ligase.

Question 15

What removes RNA primers and replaces them with DNA?

Answer 15

DNA Polymerase I.

Question 16

What happens to the DNA strands after they are built?

Answer 16

They rewind to form a double helix.

Question 17

What role does DNA Polymerase II have in replication?

Answer 17

Recognizes hydrogen bonding errors and corrects mismatches.

Question 18

What are telomeres?

Answer 18

Long, repetitive, non-coding DNA sequences at the ends of chromosomes.

Question 19

What is the function of telomeres?

Answer 19

Act as buffer zones to prevent loss of valuable genetic material.

Question 20

What are replication origins?

Answer 20

Specific sites on DNA where replication begins.

Question 21

What bonds are broken to unwind the DNA double helix?

Answer 21

Hydrogen bonds.

Question 22

What is an Okazaki fragment?

Answer 22

Short DNA fragment on the lagging strand.

Question 23

How does DNA helicase function?

Answer 23

By breaking hydrogen bonds to separate DNA strands.

Question 24

Why are RNA primers necessary?

Answer 24

DNA Polymerase III can only add nucleotides to an existing strand.

Question 25

What is a replication fork?

Answer 25

The Y-shaped region where DNA is split into two strands for replication.

Question 26

What is the purpose of DNA gyrase?

Answer 26

Prevents supercoiling by cutting and resealing DNA strands.

Question 27

How does DNA Polymerase III maintain accuracy?

Answer 27

By proofreading and correcting mismatched base pairs.

Question 28

What happens if DNA Polymerase III detects an error?

Answer 28

It removes the incorrect nucleotide and inserts the correct one.

Question 29

Why is DNA replication described as semi-discontinuous?

Answer 29

Leading strand is synthesized continuously; lagging strand discontinuously.

Question 30

What enzyme synthesizes the RNA primers?

Answer 30

Primase.