DNA Replication

Question 1

What are the steps of DNA replication?

Answer 1

1. Initiation
2. Elongation
3. Termination

Question 2

How many origin of replication are in prokaryotes? In eukaryotes?

Answer 2

• typically 1 in prokaryotes

- multiple in eukaryotes

Question 3

What happens during initiation stage? (3)

Answer 3

• DNA unwinds at the origin of replication
• SSBPs bind ssDNA
• Primase adds RNA primer

Question 4

What happens during elongation?

Answer 4

DNAP add nucleotides

Question 5

What happens during termination?

Answer 5

Reaches end or new DNA

DNAP falls off

Question 6

Where does DNA replication occur for prokaryotes? eukaryotes?

Answer 6

Prokaryotes : cell cytoplasm

Eukaryotes : nucleus

Question 7

What template is read during the process?

Answer 7

DNA

Question 8

What is the direction of the polymer formation?

Answer 8

5’ - 3’

Question 9

What direction is the template read?

Answer 9

3’ - 5’

Question 10

What polymer is formed?

Answer 10

DNA

Question 11

What monomers are used?

Answer 11

dNTPs

Question 12

What is the start signal?

Answer 12

origin

Question 13

how many origin of replications are in prokaryotes and eukaryotes?

Answer 13

prokaryotes: typically one
eukaryotes: many on a single chromosome

Question 14

What is reannealing?

Answer 14

reformation of double stranded DNA molecule

Question 15

Why is DNA always synthesized in 5’ to 3’ direction?

Answer 15

DNA polymerase need a free 3’OH group

Question 16

What is the difference between the leading strand and the lagging strand?

Answer 16

leading strand is synthesized continuously (in one go) (5’-3’).
lagging strand is synthesized in small chunks called okazaki fragments (3’-5’)

Question 17

What happens if a nucleotide (dNTPs) is added?

Answer 17

pyrophosphate is released and one phosphate remain in the phosphodiester bond

Question 18

What are the four dNTPs needed for DNA replication?

Answer 18

dATP, dTTP, dCTP, and dGTP

Question 19

Is DNA conservative or semi-conservative? Why?

Answer 19

Semi-conservative

Each parent strand ends up bonded with a new strand at the end of DNA replication.

Question 20

About how many mistakes does DNAP make?

Answer 20

1 mistake every 109 nucleotide

Question 21

What is the direction DNAP proof read?

Answer 21

3’ - 5’

Question 22

How does DNAP proof-read? (3)

Answer 22

• It forms a different angle than one that is hydrogen bonded to its pair on the other strand
• Hence, 3’OH won’t be in the correct position for extension by DNAP
• Causes DNAP to used its exonuclease activity (degrade nucleic acid) to remove the wrong nt

Question 23

What is the purpose of PCR?

Answer 23

To replicate and amplify DNA

Question 24

What are the components for PCR? (4)

Answer 24

1. Primers designed to complement the ends of each strand
2. dNTPS
3. Buffers and co-factors
4. Template DNA