Genetic influences on the age of puberty in girls have been revealed in the largest study of its kind to date. An international team led by researchers at the MRC Epidemiology Unit at the University of Cambridge found that genes can indirectly influence the age at which girls have their first period by accelerating weight gain in childhood. Other genes directly affect the age of puberty, some with profound effects, they found. The researchers studied the DNA of about 800,000 women from Europe, North America, China, Japan and Korea. More than 1,000 genetic variants – small changes in DNA – were…