[1] Department of Human Genetics,
[2] The University of Chicago,undefined
[3] 924 E 57th Street,undefined
[4] Chicago,undefined
[5] IL 60637,undefined
[6] USA e-mail: dhl@genetics.uchicago.edu,undefined
[7] Tel.: +1-773-8340525,undefined
[8] Fax: +1-773-8340505,undefined