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
-Found in the nucleus of all cells
-Controls all of the chemical changes in the
cell
- The cell’s job is controlled by DNA
Ex: Muscle, blood, nerve
-The kind of organism produced.

3. DNA is a very large molecule made up of a long
DNA molecule 3
DNA is a very large molecule made up of a long
chain of sub-units called nucleotides
Each nucleotide is made up of
a sugar called deoxyribose
a phosphate group -PO4 and
an organic base

4. Ribose is a five carbon sugar, like glucose,
Ribose & deoxyribose 4
Ribose is a five carbon sugar, like glucose,
Deoxyribose is almost the same but lacks one
oxygen atom
Both molecules may be represented by the symbol

5. The most common organic bases are
The bases 5
The most common organic bases are
Adenine
(A)
Thymine
(T)
Cytosine
(C)
Guanine
(G)

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

7. Joined nucleotides 7
PO4
sugar-phosphate
backbone
+ bases
A molecule of DNA is formed by millions of nucleotides joined together in a long chain

8. -The chains are double stranded.8
-The chains are double stranded.
-The sugar phosphate bonds are on the outside.
-The chains are held together by chemical
bonding of the bases.

9. 2-stranded DNA 9
PO4
PO4
PO4
PO4
PO4
PO4
PO4
PO4
PO4

10. The bases always pair up in the same way
Bonding 1 10
The bases always pair up in the same way
Adenine forms a bond with Thymine
Adenine
Thymine
and Cytosine bonds with Guanine
Cytosine
Guanine