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Harvard Commentaries
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Harvard Commentaries
Reviewed by the Faculty of Harvard Medical School


The Human Genome Project


September 26, 2013

Reviewed by the Faculty of Harvard Medical School

Human Genome Project and International HapMap Project

The Human Genome Project, completed in 2003, was an international effort. Coordinated by the National Institutes of Health and the U.S. Department of Energy, the project included scientists from the United States, Great Britain, Japan, France, Germany, China and others. The project's main goal was to map (sequence and understand) the 3 billion letters of human DNA, called the "human genome."

Merely spelling out the letters of human DNA did not reveal all the mysteries of life. Humans have about 10 million spots in the genome where the letters are different from one person to another. These sites are called single nucleotide polymorphisms (SNPs). We don't know what most of these changes mean in terms of human disease.

The International HapMap Project began in 2002 as an effort to catalog millions of SNPs among people from four ethnic groups: Caucasian, African, Chinese and Japanese. Scientists want to find out if SNPs can predict someone's risk for disease and how someone will respond to a particular medication.

Why "map" our genome and study SNPs?

Because your genes (and changes to your genes called "mutations") can lead to disease. Understanding how your genes work and why they change may one day help doctors treat a disease before symptoms appear. For example, genetic testing can show that you may one day get breast cancer. Knowing this early may help to prevent the disease.

All changes in DNA can be called mutations, but SNPs are a special type of mutation. Some SNPs might affect the "on/off switch" for a gene, essentially causing a disease. Researchers are trying to figure out how SNPs like this might be treated with specially made medications. Such research may lead to new therapies, including "designer drugs" or "personalized medications."

Today, a lot of treatment is trial and error. Anthony Komaroff, M.D., a professor of medicine at Harvard Medical School, recalls trying to find the right medication to treat a patient with high blood pressure. "The fifth drug we tried worked; the first four didn't." This trial and error process took about six months. In the future, research may reveal what drug is most likely to work for each person.

How long did these projects take?

When the Human Genome Project began in 1990, scientists predicted it would take 15 years to get the job done. That seemed like an ambitious goal for something so complex. Because other countries and private companies joined the effort, the project progressed at amazing speed. In June 2000, Dr. Francis Collins, the head of the National Human Genome Research Institute, and Dr. Craig Venter, of Celera Genomics, one of the private companies involved in the work, announced a rough draft of the human genome years ahead of schedule. Scientists published a final draft of the human genome in April 2003, just in time for the 50th anniversary of the discovery of DNA. The International HapMap Project was completed in 2006 after less than four years of work by researchers from around the world.

What have we learned so far?

The Human Genome Project has led to a number of interesting and unexpected findings. For one thing, scientists have found that there are fewer genes in people than expected. The estimate is now around 20,000 to 25,000 genes; before the map was created, researchers thought humans had as many as 150,000 genes.

Another surprising fact is that, according to your DNA, you are 99.9% identical to every other human on earth. That seems unlikely considering how different everyone looks and acts, but it shows that the 0.1% of the DNA that varies from person to person must be important. SNPs make up much of this 0.1%.

Currently, there are hundreds of genetic tests that can tell people if they or their children have an increased chance of getting certain diseases. Because of the Human Genome Project, more and more disease genes will be discovered, and the number of genetic tests is expected to increase substantially during the next 10 years. Right now, we are learning how the letters of our genetic code form our "alphabet." Soon, we will be able to know much more about how those letters spell words and how to correct that spelling, when necessary, to prevent or treat disease.

What's next for the Human Genome Project?

Although publishing the full sequence was the original goal, the work of the Human Genome Project is not complete. The full sequence tells us where our DNA is the same from one person to another — 99.9% is the same. Now the effort is focused on describing our genetic differences — the other 0.1%. The International HapMap Project provides an excellent starting point for these studies.

SNP differences are likely to explain why some of us are more susceptible to certain diseases. Scientists are examining patterns of SNPs in healthy people and in people with particular diseases. These studies will help to explain the causes of disease, the risks of developing disease and what we might do to protect ourselves from disease. It will take many more years of effort to work out these details, but the maps provided by the Human Genome Project and International HapMap Project will help us find our way.

 

 

 

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