The nucleotides are identical except for the base, which can be adenine, thymine, guanine or cytosine. There are chemical cross-links between the two strands in DNA, formed by pairs of bases held together by hydrogen bonds. They always pair up in a particular way, called complementary base pairing:

Thymine pairs with Adenine (A - T)
Guanine pairs with Cytosine (G - C)

These basic units are linked together to form strands by string bonds between the deoxyribose sugar of one nucleotide. These strong bonds form a sugar-phosphate Backbone.

The ends of the strand are called the 5' end at the phosphate end, and the 3' end at the deoxyribose end. The two strands of DNA are antiparallel.

All the cells store their genetic information in the base sequance of DNA nd it is this base sequence which forms the genetic code. The Genotype is determined by the sequence of bases.

	Created by Megan Samuel 7 months ago

Highers Biology (unit 1.1) Slide Set on Structure of DNA, created by Megan Samuel on 26/12/2023.