1. 1
DNA
The illustration is a ‘model’ of the double helix forming part of a DNA molecule
(Slide 14)

2. DNA -deoxyribose nucleic acid2
DNA -deoxyribose nucleic acid
A macromolecule made up of a long
chain of monomers called nucleotides.
-a sugar called deoxyribose
-a phosphate group -PO4
-an organic base

3. combine to form a nucleotide
Nucleotides 6
The deoxyribose,
the phosphate,
and one of the bases
combine to form a nucleotide
Base
deoxyribose
PO4
It is the phosphate group which gives DNA its acidic properties

4. The bases always pair up in the same way10
The bases always pair up in the same way
Adenine forms a bond with Thymine
Adenine
Thymine
and Cytosine bonds with Guanine
Cytosine
Guanine

5. The sequence of bases in DNA forms the7
PO4
sugar-phosphate
backbone
+ bases
A molecule of DNA is formed by millions of nucleotides joined together in a long chain
The sequence of bases in DNA forms the
Genetic Code

6. DNA usually consists of a double strand of nucleotides .8
DNA usually consists of a double strand of nucleotides .
The paired strands are coiled into a spiral called A DOUBLE HELIX
The sugar-phosphate chains are on the outside
(backbone) and the strands are held together by
chemical bonds between the bases

7. 2 11
PO4
adenine
cytosine
PO4
thymine
PO4
guanine
PO4
PO4

8. 9
PO4
PO4
PO4
PO4
PO4
PO4
PO4
PO4
PO4

9. Pairing up 12
PO4
PO4
PO4
PO4
PO4
PO4
PO4
PO4
PO4

10. 14
THE DOUBLE HELIX
bases
sugar-phosphate
chain

11. DNA makes copies of itself in replication16
DNA makes copies of itself in replication
Before a cell divides, the DNA strands unwind
and separate caused by an enzyme called helicase .
Each strand makes a new partner by adding
the appropriate nucleotides by DNA polymerase.
The result is that there are now two double-stranded DNA molecules in the nucleus
So that when the cell divides, each nucleus
contains identical DNA

12. 17
The strands separate
PO4
PO4

13. 18
Each strand builds up its partner by adding the appropriate nucleotides
PO4
PO4
PO4
PO4
PO4
PO4
PO4
PO4
PO4
PO4
PO4
PO4
The nucleotides are present in the nucleoplasm. The nuclear equivalent of cytoplasm
PO4
PO4
PO4
PO4
PO4

14. Replication happens very quickly at many locations at the same time
Replication happens very quickly at many locations at the same time. DNA polymerase proof reads the DNA making sure there are no mistakes.

15. Question 1 Which of the following are components of nucleotides?
(a) deoxyribose
(b) amino acids
(c) phosphate
(d) enzymes
(e) organic bases

16. Question 2 Which of the following represent a correct
pairing of bases?
(a) adenine with thymine
(b) adenine with guanine
(c) thymine with adenine
(d) guanine with cytosine
(e) thymine with thymine

17. Question 3 DNA molecules are formed from (a) organic bases
(b) amino acids
(c) deoxyribose
(d) nucleotides

18. Question 4 Which of the following are organic bases? (a) Valine
(b) Guanine
(c) Thymine
(d) Serine

19. Question 5 Replication of DNA occurs (a) During cell division
(b) before cell division
(c) at any time

20. Question 6 A nucleotide triplet codes for (a) a protein
(b) an amino acid
(c) an enzyme
(d) an organic base

21. Answer
CORRECT

22. Answer
INCORRECT