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Biology A Level > DNA Replication > Flashcards

Flashcards in DNA Replication Deck (15)
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1
Q

Why must DNA replicate?

A
  • DNA must replicate before cells divide
  • This is needed for the growth of multi cellular organisms
  • And repairing damaged tissues
2
Q

Why does DNA copy itself before cells divide?

A

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

3
Q

What does Full amount of DNA mean?

A
  • 46 chromosomes (all the genetic information)
4
Q

What is the method by which DNA replicates?

A

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

5
Q

Why is the method of DNA replication called semi conservative?

A

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

6
Q

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

A
  • There are other theories of how DNA replicates

But the semi conservative theory is the widely accepted theory

7
Q

Describe the process of DNA replication in stages?

A
  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
8
Q

Why is complementary base pairing important in DNA replication?

A
  • DNA is replicated without error/same sequence of nucleotide ids produced
  • Reduces occurence of mutations
  • allows (re)-formation of hydrogen bonds
9
Q

What is the conservation theory regarding DNA replication?

A

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

10
Q

What is the semi-conservative theory ?

A
  • ONE STRAND from ORIGINAL DNA and ONE STRAND from NEWLY formed
  • an original strand acts as a TEMPLATE for the NEW strand
11
Q

What is the theory of DISPERSIVE replication?

A

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

12
Q

What experiment provides evidence for the semi-conservative theory?

A
  • the MESELSON and STAHL investigation using bacteria
13
Q

What are mutations?

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

This may be a change to the DNA/BASES

14
Q

What causes mutations?

A
  • 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
15
Q

What are mutagens and give examples of mutagens?

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