DNA - image description

The diagram shows, in three linked illustrations, how a cell contains pairs of chromosomes, then how the chromosomes are made up of genes, and finally how the genes are made up of DNA. The top illustration shows a cell, the centre of which contains chromosomes, arranged into pairs. The second illustration looks more closely at a pair of chromosomes. These are made up of two vertical thread-like structures joined together in the middle to make an ‘H’ shape. The third illustration looks even more closely at the thread-like detail. It shows how, if unravelled, the genes are made up of DNA, which is made up of four chemicals (bases).