SECTION

8.2

STRUCTURE OF DNA

Power Notes

Parts of a

DNA molecule

Overall shape:

Double Helix

Nitrogen-

containing bases	Backbone

1...

Pyrimidines	Purines

Deoxyribose sugar

Thymine	Adenine

2.

Phosphate group

Cytosine	Guanine

Base pairing rules: A pairs with T

C pairs with G

T	A

Bonding	G	C

1. H ydrogen bonds connect the nitro-

gen containing bases in the middle

2. Covalent bonds connect the	A	T

molecules in the backbone

G C

Chargaff’s rules: The amount of A = T

and the amount of C = G