Q. In an American talk show I recently watched, a doctor, who is involved in the so-called human genome project, mentioned that findings about the human genome will make it possible to prolong life to several hundred years, make life disease-free and even come out with designer babies. What is your take on this?  What is the human genome? Are immortality and designer babies possible within my lifetime?

--Roger B., Manila

A. I hate to disappoint you, but although I consider the unraveling of the human genome as one of mankind’s greatest scientific achievements, I also think we’re still a world away from the earthshaking benefits—such as longer life expectancy and a disease-free life—that this scientific breakthrough promises to bring about. I’m willing to concede, though, that designer babies (born according to parental specifications as to height, intelligence, color of skin, eyes, etc.) are around the corner, provided civilized society allows the use of this forthcoming reproductive technology considering the ethical, legal, and social issues that it presents.

The human genome refers to the totality of DNA molecules that are present in the 23 pairs of chromosomes that each human being has. People inherit their genome from their parents (half from the mother and half from the father), and a person’s genome is unique, except for identical twins who have identical genomes.

The structure of the DNA molecules in the chromosomes can be likened to a twisted ladder that has two sides that are joined together by rungs. In the DNA molecules, the sides are made up of sugar and phosphate molecules while each rung consists of a pair of nitrogen-containing bases.

Only four kinds of bases, adenine (A), thymine (T), cytosine (C) and guanine (G) comprise the rungs, but their particular order or sequence along the ladder is highly variable. In addition, the human genome contains three billion nitrogen base pairs, which means, if you place the DNA molecules in all the chromosomes end to end, you will have a ladder that has three billion rungs. 

A person’s genome contains the instructions (in coded form) for the production of the numerous proteins that determine the physical and intellectual characteristics, as well as the physiological responses, and to a certain extent, the behavior of the person. The code for the production of a particular protein is called a gene. It consists of a segment of a DNA molecule of variable length within a chromosome. Inasmuch as the body needs to synthesize thousands of proteins and there are only 23 pairs of chromosomes, then necessarily, each chromosome contains numerous genes.

To map or determine the complete sequence of the three billion DNA bases that make up the human genome, a 13-year international collaborative effort that involved thousands of scientists known as the Human Genome Project (HGP) was started in 1990.  By 2003, the human genome has been mapped out, but up to now, very few genes have been located and identified. In fact, the actual number of human genes has not even been determined yet, although most experts estimate that the number is between 20,000 and 25,000.

Thus, scientists working on the human genome haven’t accomplished much yet. Sure they have determined the sequence of the three billion DNA bases, but locating and identifying genes, the initial step into making the genes accessible for further biological study, is far from being completed. Furthermore, work on defining, exploring, and understanding the functions of the genes that have been already identified has hardly begun.   

However, there is no doubt that further studies on the human genome will have tremendous positive impacts on medical science because every disease has a genetic component. Many diseases are inherited outright while scores are caused by the mutation (alteration) of one or more genes. Cancers are caused by abnormalities in DNA sequence. 50 percent of the risk for drug addiction is genetic. Numerous illnesses like heart disease, hypertension, and Alzheimer’s disease are not inherited per se, but the tendency to develop them is, and, so is a person’s way of responding to infection, trauma and other environmental conditions.

With the expected rapid turnover of knowledge and technology in the field of genetics within the next couple of decades, there is no doubt that significant breakthroughs in the diagnosis, treatment and prevention of diseases are in the offing. But humans are still a long, long way from immortality.

(E-mail inquiries on health matters to: medical_notes@yahoo.com or wellbeing@mb.com.ph.)