MODEL RELEASED. DNA autoradiogram. Geneticist examining a DNA (deoxyribonucleic acid) auto- radiogram. It shows a genetic sequence analysis of DNA samples. The autoradiogram is a visual record of the analysis, created on film by the reaction of small amounts of radioactivity present in each sample. Each band on the autoradiogram represents a nucleotide, the chemical unit that makes up DNA. The ladder of bands has been created by electro- phoresis, a technique that separates DNA fragments on the basis of their size. The sequence of nucleotides (adenine, cytosine, guanine, thymine) along a molecule of DNA is known as the genetic code and is unique for every individual.