How would you like to pick the color of your child’s eyes or hair before conception? Or give him or her an Albert Einstein IQ with the basketball skills of Michael Jordan? Or perhaps you’ve wished to enhance your own physical and mental abilities. I admit that I quite frequently think of how awesome it would be to have been born with killer eight-pack abs (because six isn’t enough). Although we are light years away from these ambitions, the science behind them is rapidly advancing. In fact, pre-selection of the sex of a baby is already possible.
But let me back-track to the beginnings of genetic human engineering...
I imagine the initial interest in “improving” on human design came from the idea that it could be used to cure diseases. You may have seen the movie “Bubble Boy” (or perhaps not because it was pretty lame). Quite simply, it is about a boy with a defunct immune system who has to live inside a sanitary bubble to prevent certain death by infection. Although this is a fictional story, many children do actually have this disease — severe combined immunodeficiency disease — but no bubble is needed. The first trial of gene therapy for this type of immune deficiency was attempted with two little girls in 1990. Scientists acquired blood cells from their bodies and infected them with a virus that carried a gene they lacked. Then the doctors returned the virus-laden cells into their bodies. Once inside, the virus was able to invade other cells and introduce its DNA into the DNA of human cells — in this case the gene that would restore their immunity. Although the trial resulted in a successful cure, others have been less fortunate. Four other children who underwent this therapy developed leukemia, a blood cancer, because the virus had randomly inserted its DNA into the wrong place in a wrong cell.
The previous example is known as somatic gene therapy because it involves manipulating existing cells of the body. When you mess around with genes in the egg or sperm, it is known as germ-cell gene therapy. The first highlighter-green monkey was created in this way. To do this, scientists used a jellyfish gene which encoded a fluorescent green protein and inserted this into a monkey egg. After fertilization with sperm, Andi the glowing monkey was born. When Andi was exposed to UV light, he fluoresced green. In case you’re wondering where they got the name, spell Andi backwards: Inserted DNA. How clever.
And this brings us full circle to our present capability to choose the sex of a baby. To understand how this works let me digress a bit on the genetics behind sex selection. If you remember from biology class, two sex chromosomes determine the gender of the individual: X and Y. XY combos form males while XX forms a female. Sperm can donate either an X or a Y chromosome, but the egg by default yields an X chromosome. Thus, an individual sperm ultimately determines the fate of the embryo. It stands to reason then that you could select out all of the Y sperm and always end up with XX females. Or you could take out all the X sperm, which would always result in XY males. The FDA has not approved this technology, but clinical trials are underway.
Another option, known as preimplantation genetic diagnosis, is used in conjunction with in vitro fertilization. After the fertilization of several eggs, one lucky embryo is chosen and the remaining embryos are stored frozen. The basis for selection is an embryo free of genetic defects or also gender preference of the parents. This is especially useful in detecting devastating genetic diseases, like muscular dystrophy, that, for the most part, only affect males. If a female embryo were chosen, certain forms of the disease could be bypassed. I won’t get into the ethical quandaries posed by PGD, but I will say that there are certain criteria (at least in America) which couples must meet in order to apply. The first way is by medical reason — to show that you have a family history of sex-linked genetic diseases, have a history of spontaneous miscarriages, or will be giving birth past the age of 38.
The other way is known as family balancing. Some countries permit gender selection for family-balancing purposes, but place restrictions on this act to avoid population imbalances.
In some ways I’m glad this technology wasn’t around when I was born. If it were up to my mom, surely I would have been a female (not that there’s anything wrong with that). In our lifetime, though, we probably will not see any genetically enhanced super-humans. In the meantime I’ll stick with crunches.
Ashok is a University Medical student. He can be reached at a.tholpady@cavalierdaily.com.
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