1. Higher Human Biology Unit 1 – Human Cells
DNA Structure
Higher Human Biology
Unit 1 – Human Cells

2. Location of DNA

3. Double Helix Structure

4. Nucleotides

5. Bases 4 bases Base pairing rule Adenine (A) Thymine (T) Cytosine (C)
Guanine (G)
Base pairing rule
A pairs with T
C pairs with G

6. Sugar Phosphate Backbone
Weak Hydrogen Bonds

7. Deoxyribose Sugar

8. Antiparallel Strands 5’ 3’ P O 1 2 3 4 5 P O 1 2 3 4 5 G C T A 3’ 5’

9. DNA packaged as chromosomes
DNA is located in nucleus of cell
It is extremely long and threadlike
It is wrapped around tidy protein ‘spools’