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THE LONG ROAD AHEAD OF THE HUMAN GENOME PROJECT - Page 2

© Juan C. Mendible

But, what will it tell the molecular doctors? Well, it will tell them the sequences of all the genes and the control sequences of each one of those genes; that is, those sequences that tell the expression machinery when, where and for how long to express a gene.

Since those 100,000 genes comprise roughly two percent of the one billion bases, it will also give them an incredible amount of information called junk information, since the scientists do not know their function. You may ask, if the molecular doctors are going to have all that knowledge about genes, why is there a long road ahead for the HGP? Well, it is important to keep in mind that it will not tell the scientists which genes are misspelled and even less about the paths a bad gene may take to cause disease or how to cure these diseases.

The raw result could be compared with a book that gives you a highly detailed description of every single part of your car. You will have signposts that will tell you where each part's description begins, but in the majority of the cases you will not know which part it is. Obviously you still will not have the slightest idea as to how your car (the human being) functions. Neither will it tell you how the piece (gene or control region) looks like when it is broken.

Let's take a specific example. Suppose that the HGP is finished, and you are interested in the genetic predisposition to cardiovascular diseases, say for example, myocardial infarction (MI) . You already know that cholesterol is somehow related to the development of MI. What you have to do now is to study the genes that code for the proteins involved in cholesterol metabolism in MI survivors. However, since you also know that there are other risk factors, such as; smoking, diet, ethnicity, age, sex, etc., you would have to choose a sample of patients large enough to represent the whole population, with similar demographic characteristics, and risk factors.

Next you take samples of the survivors from which to extract the DNA (blood or saliva), sequence the genes you are interested in and compare the sequences (the order of the four letters A, T, C, G) with the ones obtained from the HGP. If you find one or several gene variants (Sequences with slightly different spellings) that are common to the survivors and are not found in the normal gene, you might think that those are related to MI.

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