Cancer research. Coloured scanning electron micrograph (SEM) of a cancer cell (white) and an autoradiogram showing the genetic code of a section of DNA (deoxyribonucleic acid). Cancer is caused by unrestrained cell growth. The pattern of bands on the autoradiogram represents the sequence of bases in the genetic code. The presence or absence of particular sections of DNA, called genes, has been linked to the development of certain forms of cancer. Finding genes which are related to cancer development will allow screening to take place to detect people who are at greater risk of getting cancer.