[1] No Arizona Univ, Dept Sociol, 5 E McConnell Dr, Flagstaff, AZ 86011 USA
[2] NHGRI, NIH, Bethesda, MD 20892 USA
[3] Univ Cincinnati, Cincinnati Childrens Hosp Med Ctr, Cincinnati, OH USA
[4] Univ Cincinnati, Dept Pediat, Cincinnati, OH USA
[5] Univ Texas Austin, Sch Publ Hlth, Dept Epidemiol Human Genet & Environm Sci, Austin, TX 78712 USA