Targeted gene on a human chromosome. Composite coloured scanning electron micrograph (SEM) of a targeted gene (yellow) on one arm of a human chromosome. Each genes on a chromosomes is responsible for producing a specific protein. Chromosomes are present in the nucleus of every cell of the body. They consist of genetic material, DNA (deoxyribonucleic acid), in association with proteins. Most human cells contain 46 chromosomes, 23 inherited from the mother and 23 from the father. Diagnostic techniques are capable of fluorescently labelling regions of a chromosome associated with genetic disease. Magnification: x13,550 at 6x6cm size.