American physician who with P. A. Jacobs helped show that Klinefelter's syndrome was linked to one of the sex chromosomes. This was one of the first diseases shown to be either "x-linked" or "ylinked." Linkage to a sex chromosome is important because, in males, there is only one of each sex chromosome. This means that a genetically recessive disease or trait will not appear in women but will appear in men because men lack a second x chromosome to mask the disease.