Sponsored by the U.S. Department of Energy Human Genome Program
Human Genome News Archive Edition
Human Genome News, July 1990; 2(2)
NIH National Center for Human Genome Research
A quick glance around any public gathering will attest to the physical diversity of the human population. In most groups of people, some will be tall, others short; some will have brown eyes, and others blue. These physical attributes are largely determined by genes-packets of the chromosomal genetic material, DNA.
The complete human DNA, collectively called the human genome, is made up of about 3 billion chemical subunits called nucleotides. The task of the Human Genome Project is to map all the genes on human chromosomes and to determine the order, or sequence, of the 3 billion nucleotides. As scientists begin to map and analyze the molecular details of the human genome, the question is often asked, Whose genome is being used?
Are scientists using just one genome?
In many ways, describing the anatomy of the human genome will be similar to studying the human heart or the human brain. While there are small differences from person to person in the size and shape of these organs, most key characteristics are the same. Although human beings are distinct from one another, they are really very similar in most biologically important respects, says Mark Guyer, Assistant Director for Program Coordination, National Center for Human Genome Research (NCHGR). That's what makes us human. So the map of the human genome can really be based on information collected from many different people. And most of the information in that map will pertain to everyone.
Geneticists estimate, for example, that any two people are about 99% similar in their genetic makeup. The tiny differences between any two people rest in only 2 to 10 million (out of the 3 billion total) nucleotides, an amount that computes to less than 1% of their total DNA. Because these small differences vary from person to person, says Guyer, it doesn't matter whose genome it is. Furthermore, it doesn't matter how many different genomes are used.
How will various genomes be integrated into one reference map
Eventually, scientists will map, or establish distinctive genetic landmarks, from one end of a chromosome to the other and add that information to the genetic map of the entire human genome. This complete map will become the reference to which researchers will compare DNA taken from a variety of people as scientists look for disease genes and other important genetic regions located on chromosomes. A particular region on a chromosome, for example, may be found to contain information about height. Although the genetic content of that specific site may change slightly from person to person, the location of the site will be the same in each person's genome.
Because studying the entire 6-foot stretch of human DNA is a huge project, scientists are tackling the genome one chromosome at a time. Nevertheless, analyzing the genetic content of just one chromosome is an enormous task for a single research group, so many scientists are studying portions of chromosomes. The complete map for a single chromosome will, therefore, be derived from samples collected by researchers in many different laboratories from unrelated individuals.
David Ledbetter and his colleagues at the Baylor College of Medicine, for example, are mapping the sex chromosome X and chromosome 17. We collect DNA from patients who come into our clinic for genetic testing, says Ledbetter, so each sample is from a different and unrelated person. Our cell culture collection contains a number of different human genomes.
According to David Schlessinger, Director of the Center for Genetics in Medicine at Washington University in St. Louis, The ultimate goal of the genome project is to have the technology and ability to check parts or all of many genomes. We will analyze one genome relative to another, and that's part of the interest in this project.
Referring to the donor of the X-chromosome region Schlessinger's group is studying, he states, The identity of the donor is locked away . . . . that individual is the genetic equivalent of the unknown soldier.
The electronic form of the newsletter may be cited in the
Human Genome Program, U.S. Department of Energy, Human Genome News (v2n2).
The Human Genome Project (HGP) was an international 13-year effort, 1990 to 2003. Primary goals were to discover the complete set of human genes and make them accessible for further biological study, and determine the complete sequence of DNA bases in the human genome. See Timeline for more HGP history.
Published from 1989 until 2002, this newsletter facilitated HGP communication, helped prevent duplication of research effort, and informed persons interested in genome research.