DNA Replication

Question 1

Why must DNA replicate?

Answer 1

• DNA must replicate before cells divide
• This is needed for the growth of multi cellular organisms
• And repairing damaged tissues

Question 2

Why does DNA copy itself before cells divide?

Answer 2

DNA copies itself before cells divide so that each cell has the full amount of DNA

Question 3

What does Full amount of DNA mean?

Answer 3

• 46 chromosomes (all the genetic information)

Question 4

What is the method by which DNA replicates?

Answer 4

the method by which DNA replicates is known as the SEMI CONSERVATIVE method

Question 5

Why is the method of DNA replication called semi conservative?

Answer 5

The method by which DNA replicates is known as semi conservative because each new DNA molecule is made of 1 old DNA strand and 1 new DNA strand

Question 6

Are there other theories besides the semi-conservative theory as to how DNA replicates?

Answer 6

• There are other theories of how DNA replicates

But the semi conservative theory is the widely accepted theory

Question 7

Describe the process of DNA replication in stages?

Answer 7

1. DNA helix UNZIPS DNA helicase
2. Hydrogen bonds break
3. Each single strand acts as a template for a new strand
4. Free - floating nucleotides bind to each template strand by specific base pairing (A-T C-G)
5. New nucleotides are joined together by DNA POLYMERASE
6. Hydrogen bonds form between the bases on the original and new strand
   EACH NEW DNA STRAND HAS 1 ORIGINAL STRAND AND 1 NEW STRAND

Question 8

Why is complementary base pairing important in DNA replication?

Answer 8

• DNA is replicated without error/same sequence of nucleotide ids produced
• Reduces occurence of mutations
• allows (re)-formation of hydrogen bonds

Question 9

What is the conservation theory regarding DNA replication?

Answer 9

The conservative theory :
- the ORIGINAL DNA molecule stayed intact and that a new molecule exactly the same as the first would be built up entirely from NEW NUCLEOTIDES

Question 10

What is the semi-conservative theory ?

Answer 10

• ONE STRAND from ORIGINAL DNA and ONE STRAND from NEWLY formed
• an original strand acts as a TEMPLATE for the NEW strand

Question 11

What is the theory of DISPERSIVE replication?

Answer 11

Dispersive replication:
original DNA molecule would break down
Nucleotides would be replicated
Then the 2 new identical molecules would be made with a mixture of old and new

Question 12

What experiment provides evidence for the semi-conservative theory?

Answer 12

• the MESELSON and STAHL investigation using bacteria

Question 13

What are mutations?

Answer 13

• a MUTATION is a RANDOM change due to the GENETIC MATERIAL

This may be a change to the DNA/BASES

Question 14

What causes mutations?

Answer 14

• mutations may occur during DNA replication
  This may happen when the DNA is replicating before nuclear division (by either mitosis or meiosis)
• mutations may also be caused by certain mutagens

Question 15

What are mutagens and give examples of mutagens?

Answer 15

- mutagens are any substance that increase the chance of a mutation 
E.g.:
- TAR (found in tobacco)
- UV LIGHT 
- X-RAYS GAMMA RAYS