A sperm donor in Michigan passed a rare and serious genetic disease to five children born to four couples, doctors are reporting today. The doctor who discovered the cases said that all four couples were clients of the same sperm bank. That bank, the doctor added, assured him that it had discarded its remaining samples from the man and had told him he could no longer be a donor. It is not known how many children the donor had fathered, whether he knew he carried the disease before he donated sperm, or whether the bank had informed him of his...