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DNA chips

Scientists can use DNA chips to look at just one or some of our 24,000 different genes. To make a DNA chip, scientists cram 'reference fragments' of DNA (for example gene fragments known to be altered in breast cancer) on to a piece of glass the size of a thumbprint. They can then investigate which versions of the genes - alleles - are present in a sample of DNA from a patient, simply by applying the sample to the chip and seeing if they react with the reference fragments.

A DNA chip array.
A DNA chip array.
US Department of Energy Human Genome Program (

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