It’s a miracle,” she told me. “We can now have a baby that won’t have Huntington’s disease. I thought I’d never be able to have any kids — because of the disease.” Her father had died from this disorder, which results from a gene mutation. She feared that she might have the mutation, too. But she was too scared to undergo testing for it. She also worried that if she had it, she might pass it on to her children.
This disease causes severe neurological and psychiatric problems, and eventual death at around the same age as one’s parent died of it — usually in one’s 40s or 50s. If a parent has the disease, each child has a 50% chance of inheriting it.
Woody Guthrie, the singer and songwriter, died of this illness. His children then had to debate whether they wanted to know if they, too, had the lethal mutation. His son, Arlo, for instance, decided not to find out. Many such offspring feel that to undergo this genetic test is to risk “getting a death sentence,” i.e., while they may feel fine, they know they have a mutation that will kill them.
The woman with whom I spoke was afraid to learn if she had this gene. But she wanted to make sure that her children did not get it.
Luckily, a relatively new procedure — pre-implantation genetic diagnosis, or PGD — allows doctors to test embryos before they are implanted into a woman’s womb, to help ensure that certain gene mutations are not passed on. Using In Vitro Fertilization, sperm fertilize eggs outside the womb, creating embryos. When the embryos are a few days old, one cell is removed and can be tested for hundreds of genes.
This woman struggled with what to do. She feared she would be playing God. But she decided to undergo the procedure. The doctor told her that embryos without the mutation were implanted inside her. He did not tell her whether he had identified any embryos with the mutation. Thus, she was able to have a child free of the gene mutation that would cause Huntington’s disease, tremendously relieving her and her husband of worries. She still does not know if she has the bad gene herself.
But this procedure is raising myriad complex ethical and social issues. It can eliminate gene mutations for untreatable diseases that kill infants and adults. But it can also be used to select embryos based on other genetic factors.
Many parents decide that they want to choose, for instance, their future child’s gender, and many doctors now use this technology to do so. At some point in the future, tests will no doubt be marketed for genes that, companies will claim, are associated with behavioral traits such as intelligence, sexual orientation, possibly even perfect musical pitch, or physical characteristics like height, blond hair and blue eyes. Many of these claims will be highly questionable.
Among diseases, Huntington’s is rare in that the gene mutation predicts the disorder. But for most people, common diseases and traits result from combinations of both nature and nurture — multiple genes, along with various environmental and other factors. So, a particular mutation may contribute in some small way toward a disease or trait, but it would not be the sole determinant. A gene mutation might double your chance of getting a particular disease; say your risk may rise from 5% to 10%, but you would still have a 90% chance of never getting the disease.