Human chromosomes in the nucleus

Condensed human chromosomes superimposed on an image of a whole nucleus, whose chromosomes are not condensed, all stained with a blue fluorescent dye. The green fluorescent dye stains the centromeres of the pair of X chromosomes that carry the Duchenne muscular dystrophy gene. The red dye highlights a cosmid probe that binds to part of the intact (normal) muscular dystrophy gene itself. These chromosomes are thus from a normal female, as the probe has bound to both X chromosomes. In a female carrier of Duchenne muscular dystrophy, where there is a deletion within the gene, this red signal would be missing from one of the pair of chromosomes. Boys (who have only one X chromosome) can inherit the disorder from their mother if an X chromosome containing the defective gene is passed to them.

Dr John Crolla, Wessex Regional Genetics Laboratory, Salisbury District Hospital.