Describe the structure of DNA and the possible base pairs it contains.

DNA is a molecule made up of thousands of atoms and is very long and thin. It is made up of two twisted chains or "backbones." A double helix is the term for this structure. It would appear like a ladder if you could straighten a DNA molecule out. The ladder's "rungs" are built up of two smaller molecules called bases.

adenine (A) and thymine (T) join together = A-T

guanine (G) and cytosine (C) join together = G–C

DNA is a molecule with a double helix structure. This means that it is shaped like a twisted ladder. The backbone of the molecule is made up of two long chains that spiral around each other. The struts of the ladder are base pairs, which are made up of two bases joined together.

There are four bases: adenine (A), cytosine (C), guanine (G) and thymine (T). These can only join together to form two possible base pairs: adenine–thymine or cytosine–guanine.