Biological Molecules Nucleic Acid 3.1.5.2 DNA Replication

Question 1

Name the Scientists who confirmed that the Semi-conservative model of DNA replication was the valid model.

Answer 1

Matthew Meselson

Franklin Stahl

Question 2

Identify the method of DNA Replication

Answer 2

Conservative DNA Replication

Question 3

Define nuclear division

Answer 3

The process by which the nucleus of a cell divides during cell division.

Question 4

Identify the type of DNA Replication

Answer 4

Dispersive DNA Replication

Question 5

Identify the method of DNA Replication

Answer 5

Semi-conservative DNA Replication

Question 6

What is the function of DNA Helicase?

Answer 6

An enzyme that breaks the hydrogen bonds between the base pairs of a DNA double helix.

Question 7

Describe the experiment that Meselson and Stahl carried out to confirm the semi-conservative method of DNA replication

Answer 7

• Grow E. coli bacteria in ₁₅N (heavy isotope), which is assimilated into its base pairs, causing it to have heavy DNA. Take a sample of this and ‘normal’ ₁₄N grown E.coli
• Allow ‘heavy DNA’ E. Coli to divide once in ₁₄N growth medium and take a sample.
• Allow E. Coli to divide once more in 14N growth medium and take another sample.
• Remove DNA from each sample and perform gradient density centrifugation.
• Check the mass of DNA present in each sample.

Question 8

Define cytokinesis

Answer 8

The process by which the whole cell divides (after nuclear division)

Question 9

Describe the process of semi-conservative DNA replication.

Answer 9

• DNA Helicase breaks the hydrogen bonds joining the complementary base-pairs of the parent strand, forming 2 template strands.
• Free nucleotides bind to their specific base pairs on each template strand.
• DNA Polymerase joins the free nucleotides by forming phosphodiester bonds.

Question 10

Name the 3 models of DNA replication proposed by James Watson and Francis Crick.

Answer 10

Conservative Replication

Semi-conservative Replication

Dispersive Replication

Question 11

What is the function of free DNA nucleotides in DNA replication?

Answer 11

To bind to a separated strand of parent DNA to form a new complementary strand of daughter DNA.

Question 12

What is the function of DNA Polymerase?

Answer 12

An enzyme that joins the free daughter nucleotides bound to the parent template strands by creating phosphodiester bonds between nucleotides.

Question 13

What is required for DNA replication to take place?

Answer 13

DNA to be copied

Free DNA nucleotides

DNA Polymerase

DNA Helicase

Energy to drive the process

Question 14

What is meant by ‘semi-conservative’ DNA replication

Answer 14

DNA replication whereby each new DNA molecule contains one of the original DNA strands.

Question 15

Identify the missing label

Answer 15

Replication Fork

Question 16

name 2 enzymes involved in semi conservative replication of DNA

Answer 16

DNA helicase

DNA polymerase

Question 17

Describe the ROLE of the 2 enzymes in DNA replication

Answer 17

1. Helicase - breaks H binds
2. DNA polymerase joins DNA nucleotides together to reform phosphodiester bond

Question 18

give 2 features of DNA and explain how each is important for semi conservative replication

Answer 18

1. weak H bonds to allow unzipping of 2 strands
2. CBP to allow for accurate replication
3. Two strands so both can act as template