Puberty has a clear physiological signpost in girls: sooner or later, they have their first period. That's been a critical part of identifying genes that influence when puberty starts in girls, but it wasn't clear whether those genes also affected boys the same way.
To find out, researchers -- led by University of Cambridge geneticist John Perry -- teamed up with genetics testing company 23andMe to screen for genetic differences associated with the age when men using the service had started puberty. They couldn't ask guys how old they were when they'd had their first period, but they could ask how old they were when their voice broke.
23andMe users were offered the question when they logged on to the site. More than 55,000 men answered it. Comparing their answers to their genetic data revealed 11 genetic differences correlated to the timing of male puberty; comparing those data to similar studies on women showed that 9 of the differences also affect the timing of female puberty. And that means to a large degree, both sexes are using the same instructions to run slightly different puberty programs.
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