I’ve written before about the genetic code and how it writes a description of each of us using an alphabet of only four letters: the four bases that are contained in deoxyribonucleic acid (DNA), adenine (A), guanine (G), cytosine (C) and thymine (T).
Every organism has different proportions of these four bases. Two strands of DNA run parallel to each other, but in opposite directions, forming the famous “double helix.” In the centre of the molecule, weak chemical interactions between the bases hold the strands together. Adenine (A) always forms bonds with thymine (T), while cytosine (C) always binds with guanine (G). The sugar and phosphates that are also part of DNA form the backbones of the two strands, on the outside of the helix.
When DNA replicates itself, the double helix unzips, and because A can only bond with T and C can only bond with G, the new strand that forms on each half of the unzipped helix is a perfect copy, 999,999,999 times out of a billion. By overseeing the production of proteins, which form the more complex structures of our bodies, our DNA, contained in every cell, controls our physical make-up.
While there are variations from individual to individual, there is also an underlying structure, a basic order of the four bases, that determines that we are human and not, say, a chimpanzee (whose genetic structure is very, very similar to ours).
In humans, this basic sequence is three billion bases long. This is the human genome, the totality of genes making up humanity’s common heredity; and biologists worldwide are now involved in an effort to list that sequence of bases from start to finish.
This is not a small project. It’s the biologist’s equivalent of the Apollo moon project, with an estimated cost of $3 billion. Yet the benefits are expected to be immense.
The Human Genome Initiative had its birth in 1984 when Robert Sinsheimer, chancellor of the University of California at Santa Cruz, was thinking about large telescopes and how much they cost, and about ways to put Santa Cruz on the biological science map. He came up with the idea of sequencing the human genome, and in 1985 called together a group of scientists for a workshop.
Generally, at that initial meeting, scientists were skeptical, for two reasons. Some felt that we wouldn’t learn enough to make the effort worthwhile, given that 90 percent of the human genome may have no function. They also felt that the project was so huge that it would swallow up money that might be better spent in other areas of research.
Others felt we would learn too much, and feared that knowing the complete human genome could lead to genetic discrimination by employers and insurance companies or even to a new Nazi-like program aimed at developing a superior race.
Despite these concerns, the initiative has proceeded, until today there are groups working on it worldwide, although the largest effort (and coordination of the project) is in the United States. For those scientists involved, the benefits outweigh the hazards.
What are those benefits? For one, a complete listing of human DNA would make it possible to identify genetic diseases rapidly and accurately by comparing DNA sequences from the tissue of an affected person with a reference sequence in the data bank. Another benefit, possibly even more important, would be the ability to see how ordinary cells affected by disease or aging differ from the genetic norm. This greater understanding of the basis of disease would almost certainly lead to more effective treatment.
Most basic of all, perhaps, having a complete map of the human genome could tell scientists more about how we became human in the first place: how our genes have evolved.
There are less direct benefits, too. Like the space program, the Human Genome Initiative will be a powerful driving force in the development of new technology and research techniques. It may very well completely revolutionize the field of biology.
Yet you can see where the ethical considerations arise. Very few people will meet the standards of the “perfect” human outlined by the completed genome. Could those who don’t match up face discrimination of one kind or another? Will men and women become obsessed with finding a genetically perfect mate? Will abortions multiply as children tested in the womb are found to be genetically impairedmaybe just by having brown eyes instead of blue?
Such questions arise with every expansion of human knowledge. Some people argue that the very existence of such questions means the initiative should not go ahead, but I can’t agree with that: if there’s one thing that truly makes us human (written in our genes, perhaps?), it’s our desire for knowledge. To turn our backs on that questioning spirit would be to turn our backs on our humanity and to give up on our future.
The Human Genome Initiative, like all of science, is an expression of humanity’s thirst for understanding. What will be learned and what will come of it can’t even be predicted now–and that’s what makes it exciting.