DNA Replication

Question 1

Which 4 enzymes are involved in DNA replication?

Answer 1

• DNA Helicase
• DNA Polymerase
• DNA Primase
• DNA Ligase

Question 2

What can DNA Polymerase do?

Answer 2

Accurately copy a DNA template

Question 3

How does DNA Polymerase build a DNA strand

Answer 3

• First DNA strand is unzipped and becomes single stranded
• With help of other enzymes, it adds free nucleotides to DNA template

Question 4

What type of cells contain DNA Polymerase?

Answer 4

All cells (prokaryotic and eukaryotic cells) possess different versions of DNA Polymerase

Question 5

What role does DNA Polymerase serve in the body?

Answer 5

Helps with replication and repair of DNA

Question 6

Which direction does DNA Polymerase work in?

Answer 6

5’ to 3’ direction

Question 7

What does DNA Polymerase require to attach to DNA strand and begin building DNA strand and why?

Answer 7

A primer (RNA) is needed.
DNA Polymerase can only add nucleotides to and existing strand, thus RNA acts as primer.

Question 8

What is role of DNA Primase?

Answer 8

To attach short lengths of RNA that bind to DNA strand.
Enables DNA Polyemrase to attach and build strand.

Question 9

What is the role of DNA Ligase?

Answer 9

• To join together fragments/ends of DNA strands.
• Acts as glue for DNA.
• They form phosphodiester bonds between nucleotides to join strand.

Question 10

Desrcibe the 1st process of DNA Replication

What happens to double helix?

Answer 10

• The unfloding and unwinding of DNA double helix at replication origins

Question 11

What are replication origins?

Answer 11

Various points along the chromosome where DNA is unwound and unfolded.

Question 12

Describe 2nd step in DNA Replication

What happens to double strand?

Answer 12

• Enzyme helicase separates the two DNA strands by breaking hydrogen bonds
• The point of opening is called replication fork

Question 13

Describe 3rd step of DNA Replication.

Primers

Answer 13

• DNA Primase brings short strand of RNA.
• This binds to DNA strand at points where DNA strand is separated.

Question 14

Describe 4th step in DNA Replication.

Leading strand

Answer 14

• The leading strand (5prime to 3prime) is synthesized continuously as DNA Polymerase can work in 5prime to 3prime direction.

Question 15

Describe 5th step in DNA replication

Lagging strand - Part I

Answer 15

• Lagging strand (3prime to 5prime) is synthesized discountinuously. It is built bcakwards.
• Using an RNA Primer, DNA Polymerase synthesises a short section of DNA called Okazaki fragments.

Question 16

Describe 6th step in DNA Replication

Lagging strand - Part II

Answer 16

• When done, RNA primers are removed. DNA polymerase moves to next primer.
• Gaps left by Polymerase are filled by DNA Polyemrase.
• Segments of strands created are joined by DNA Ligase.