When scientists first read out the human genome 15 years ago, there were high hopes that we'd soon understand how traits like height are inherited. It hasn't been easy. A huge effort to find height-related genes so far only explains a fraction of this trait.
Now scientists say they've made some more headway. And the effort is not just useful for understanding how genes determine height, but how they're involved in driving many other human traits.
At first, these problems didn't seem to be so complicated. The 19th-century monk Gregor Mendel discovered that traits in his garden peas, like smoothness and color, could be passed predictably from one generation to the next.
But
Joel Hirschhorn, a geneticist at Boston Children's Hospital and the Broad Institute, says it became evident that most stories of inheritance were not so simple. Height turns out to be a prime example.
"People's height didn't behave like Mendel's peas," Hirschhorn says. "It wasn't like they you had two tall people and they'd either have a tall [child] or a short [child]. Often the child was partway between the parents."
Scientists explained this 100 years ago, when they realized that height was influenced by many genes, and each makes a small contribution.
So when the human genome was sequenced, scientists like Hirschhorn thought they could plumb that data to track all the height genes, and finally understand how height — and in fact most other human traits — are shaped by our genes.
That effort started slowly. But now, Hirschhorn says. "for height there are about 700 variants known to affect height, each of them usually with a pretty small effect on height, usually like a millimeter or less."
That massive global effort has involved studying the genes of more than 700,000 volunteer subjects. Even so, the traits they've found only explain about a quarter of the inherited height factors.
www.npr.org
