DNA

- DNA- polynucleotide- lots of nucleotides joined together

- Each nucleotide= pentose sugar (5 carbon atoms), a phosphate group and a nitrogenous base.

- The sugar in DNA nucleotides is a deoxyribose sugar

- Each nucleotide has the same sugar and phosphate. The base on each nucleotide can vary though.

- There are four possible bases- adenine, thymine, cytosine and guanine.

- Two polynucleotide strands join together to form a double-helix

- The nucleotides join up between the phosphate group of one nucleotide and the sugar of another, creating a sugar-phospahte backbone.

- Two DNA polynucleotide starnds join together by hydrogen bonds between the bases.

- Each base can only join with one particular partner- this is called specific base pairing.

- Adenine always pairs with Thymine and Guanine always pairs with Cytosine

- The two strands wind up to form the DNA double helix.