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Scientists are conducting a series of mobile DNA tests in Northern Ireland in a search for the AIP gene, which is known to cause abnormal growth of the pituitary gland.
Those who carry the gene may not experience any health problems, although a condition known as acromegaly could develop, in which a benign enlargement of the pituitary gland causes excess growth of muscles, cartilage and bones.
The particular gene is related to the case of Charles Byrne, born in the 18th century and known as the Irish giant for having grown above seven-and-a-half-feet tall. According to genetic calculations, living patients who carry the genetic mutation have been identified as sharing a common ancestor with Byrne, which can be traced back to the 6th century.