How are chromosomes ‘painted’?
Your 23 pairs of chromosomes contain around 24,000 pairs of genes. FISH – fluorescent in situ hybridisation – can be used to ‘paint’ chromosomes. Scientists prepare chromosomes on a microscope slide, tag a copy of the gene they want to find with a fluorescing dye and add it to the slide. Under a special microscope, the same gene shows up as a brightly coloured dot on the chromosome.