Department of Genetics, Dartmouth Medical School, Hanover, New Hampshire, USA.|Department of Genetics, Dartmouth Medical School, Hanover, New Hampshire, USA.|Department of Genetics, Dartmouth Medical School, Hanover, New Hampshire, USA.|Department of Genetics, Dartmouth Medical School, Hanover, New Hampshire, USA.|Department of Genetics, Dartmouth Medical School, Hanover, New Hampshire, USA.|Department of Genetics, Dartmouth Medical School, Hanover, New Hampshire, USA.