Human Genetics and Reproduction Part 1

About the development of science in the fields of genetics and reproduction. This part focuses specifically on the case of Down Syndrome and expecting mothers.


Just before W.W.II, there was a move afoot among the world's few nuclear physicists to halt research and leave the secrets of nuclear energy undiscovered. Theirs was a terrible dilemma, for scientists are dedicated to truth, not consequences--even when the consequences include nuclear death. Even after open warfare spared them that choice, they kept strategic findings secret with great reluctance. Today, we live half an hour from Armageddon, the upshot of their curiosity.

Biologists will soon face similar quandaries. Over the past 40 years, they've cooked up an arsenal of techniques that could generate the ultimate disease, produce armies of zombie clones, manufacture test-tube babies, even create a bestiary of griffins, sphinxes, centaurs, manticores, and Ganeshas. Properly applied, the same methods promise healthier babies, more bounteous agriculture, better wines, cheaper drugs, and industrial processes that transform anything into almost anything else. To reap these benefits, we face novel, often disturbing decisions.

Consider the predicament of an expectant mother in her 40s. She has 1 chance in 60 (the odds are 1 in 1,500 for a mother in her 20s) of bearing a child afflicted with Down's syndrome. Should she lose the gamble, her child will suffer extreme mental retardation, often accompanied by other internal defects that bring early death. Ten years ago, she had little choice in the matter. Today she can avoid the risk through amniocentesis, a procedure developed by Dr. Henry L. Nadler of Children's Memorial Hospital in Chicago. During her fourth month of pregnancy, her doctor takes a small sample of the amniotic fluid in her uterus. Normally, cells flake off the growing fetus and are found floating in the amniotic fluid. The doctor grows these, then counts their chromosomes under a microscope. One extra chromosome #21 is proof positive of Down's syndrome.

Down's syndrome is only one of more than 1,800 congenital defects. Many are severe: cystic fibrosis (progressive lung damage and defective pancreatic function produce severe digestive disorders and breathing difficulties; half the afflicted children die before they're 14); Tay-Sachs disease (severe progressive mental retardation and blindness, usually fatal in early childhood); hemophilia (inability to form blood clots; even the smallest cut continues to bleed until the wound heals); muscular dystrophy (muscular weakness appears, usually in boys between ages 3 and 10, then develops into paralysis); sickle-cell anemia (malformed red blood cells carry insufficient oxygen to tissues, causing weakness, dizziness, sometimes brain damage and death). Some are monstrous: cridu-chat (faulty development of larynx, so the child's cries sound like those of a cat; severe mental retardation, inability to speak, characteristic small head and distorted features); anencephaly (almost no brain, and consequently very small head); hydrocephaly (brain and head swollen to abnormally large size by excess fluids). Through genetic counseling, prospective parents can find out the risk of their child's suffering deformities. In many cases, prenatal tests like amniocentesis can let them know early enough in pregnancy to abort, if they so choose.

Some consider such abortions murderous. Others, like Dr. Robert Sinsheimer of Caltech, maintain that "every child has a right to be born whole and well." Parents faced with this difficult decision might profit from a visit to a children's hospital that cares for the congenitally deformed.

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