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Tracking genes in families

Researchers can track down genes involved in genetic conditions by looking at DNA from affected families. They study how the condition is passed on from one generation to the next, looking for a piece of DNA that is inherited along with the condition. During the search for the gene involved in Huntington disease, for example, a DNA fragment from chromosome 4 gave researchers the clue they needed.

DNA analysis of a genetic condition. Each lane shows a different person's DNA: the affected children all have a band in common with their affected father (arrowed), while the unaffected child does not.
DNA analysis of a genetic condition. Each lane shows a different person's DNA: the affected children all have a band in common with their affected father (arrowed), while the unaffected child does not.
Dr R Elles, Regional Molecular Genetics Laboratory, St Mary's Hospital, Manchester

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