Structure of DNA

• DNA is a polymer composed of 2 polynucleotide chains joined together by hydrogen bonds
• A-T is joined by 2 hydrogen bonds
• C-G is joined by 3 hydrogen bonds
• The polynucleotide chains run antiparallel to each other
• The sugar-phosphate backbone is on the outside of the molecule
• DNA molecules are very long and thin, and are tightly coiled within the chromosome
• At one end of a sugar-phosphate backbone is carbon atom number 5 (C5) of a sugar unit. This is the 5' end of the molecule, and at the other end is 3' (C3)
• How is DNA suited to its function?

  -it is a very stable molecule and its information content passes essentially unchanged from generation to generation

  -it is a very large molecule and carries a large amount of genetic information

  -the two strands are able to separate, as they are held together by hydrogen bonds

  -as the base pairs are inside the helix, the genetic information is protected
• What is the pentose sugar in DNA?

  Deoxyribose