After technicolour treatment the normal complement of 23 chromosome pairs from a human cell looks more like a clew of psychedelic glow worms. Composed of ordered lengths of DNA, each chromosome pair has a characteristic length and shape. Inherited genetic disorders and cancer can cause them to subtly or wildly distort. Fluorescence in situ hybridisation (FISH) colour-banding highlights a precise bar-code pattern shared by normal chromosome pairs, a boon for the cytogeneticists who match them up and check them. Can you see pairs? Fragmented gibbon DNA tagged with fluorescent dyes is here shown to bind specifically to regions of human DNA with a similar sequence. Juxtaposition of the dyes shows up as different colours under confocal microscopy producing a striped bar-code pattern. Where the pattern is disrupted, chromosomes have rearranged. This technique can be used to help diagnose certain diseases like leukaemia informing the appropriate choice of treatment.
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