At a genetic level, human beings are programmed to survive. Deep down in our cells, in the coiled coding of our DNA, we carry all the information our bodies need to see us through this life and ensure our genetic material carries on to the next generation. As you might have noticed from our position atop the food chain, we don't have to struggle that much anymore to carry out the necessities. So in our spare time, we've thrown our brains at a range of other problems. How can we secure our food supply? How can we fly through the air? How can we teach a dog to shake hands with us?
OK, so some of our goals aren't that lofty. But the inevitability of death and our desire to keep going in the face of every obstacle has led countless humans to pursue the medical field. Granted, "science" hasn't always played a role in our attempts to understand our bodies, but over the last few centuries, we've been on quite a roll. In 1868, Friedrich Miescher discovered the presence of DNA, and in 1953, James Watson and Francis Crick discovered its molecular structure, with the help of Maurice Wilkins, Rosalind Franklin, Erwin Chargaff and Linus Pauling.
In the years that followed, scientists have learned a great deal about how this genetic code dictates who we are. In 1990, the U.S. Department of Energy and the National Institutes of Health decided to map our accumulated genetic material, which we call a genome. These researchers formed the Human Genome Project (HGP), and the United Kingdom, Japan, France, Germany, China and other nations soon joined the effort.
The project set out to accomplish some intimidating goals: to identify human DNA's 20,000 to 25,000 genes and to determine the sequences of the 3 billion chemical base pairs in DNA. In 2003, after 13 years of research, researchers completed this genomic map. Today, the project's scientists continue to analyze the stored data -- a job that will keep them busy for years to come.
But even with a completed genomic map, many questions remain. It's one thing to know the human genome, but another to know what factors dictate how it relates to our observable characteristics or phenotype.
Who will step up and tackle this challenge? Find out on the next page.
Mapping the Human Epigenome
Think of our genes as a code that translates into a finished human being, much like a coded manuscript would translate into a readable text. Now imagine what that text might look like if you went in and covered up various words and phrases so they couldn't be translated. The finished text might be better because of this editing, but it could also be worse or even unreadable. It all depends on what words were kept out of the final copy.
This is where epigenetics comes into play. The word literally means "above the genome" and relates to the changes that occur between the genome and the phenotype. Epigenetic changes don't alter the genes, but they do affect the way they're expressed.
There are several different kinds of epigenetic changes, but the one we understand the best is methylation. This process involves carbon and hydrogen bundles (CH3) called methyl groups, which bind to the DNA and essentially cover up genes so they can't activate, much like the covered-up phrases in our coded manuscript. Some of those inactive genes could cause disease. In fact, an estimated 50 percent of the reasons for a given disease can be attributed to genetic factors [source: Bhattacharya]. Others parts of the genome, such as tumor-suppressing genes, help to prevent cancer. Epigenetic changes can alter the balance, though. These changes can occur due to several different environmental causes, from the contents of our diet to how stressful our childhood was. To learn more about these changes, read How Epigenetics Works.
So thanks to the Human Genome Project, we know where all these genes are, but we don't know which genes are expressed in different tissues and what chemical changes switch them on and off. This is where HGP's successor comes in. In 2003, scientists from the United Kingdom's Wellcome Trust Sanger Institute in Cambridge and the biotechnology company Epigenomics formed the Human Epigenome Project (HEP) with the intent of mapping the way methyl groups affect DNA in the human genome. If successful, HEP could enable doctors to better diagnose diseases and advance the field of pharmacogenetics by allowing researchers to develop drugs capable of directly changing the way genes are expressed.
The group set out to map methylation patterns in the human genome, using 200 samples from major human tissues. They were committed to defining methylation variable positions (MVPs) on the X chromosome, Y chromosome and chromosomes 1 through 22. So far, they've completed chromosomes 6, 20 and 22 and plan to continue to map the chromosomes in batches and release them to the public 120 days after each batch has been completed. In recent findings, HEP scientists have observed that DNA methylation remains more stable over the course of an individual's life than previously thought.
Researchers at HEP still have a long way to go toward achieving their goal of mapping the human epigenome, but they hope to gain additional funding and attract involvement from even more researchers. In 2008, the United States government threw its hat into the epigenetic ring, allocating $190 million for the National Institutes of Health's (NIH)'s Roadmap Epigenomics Program. The NIH also awarded grants of up to $12 million to U.S. epigenome mapping centers, epigenomics data analysis and coordination projects, technology development in epigenetics and the discovery of important epigenetic marks in mammalian cells [source: NIH]
Explore the links on the next page to learn more about genetics.
Related HowStuffWorks Articles
More Great Links
- Bhattacharya, Shaoni. "Human gene on/off switches to be mapped." New Scientist. October 2003. (Oct. 3, 2008)http://www.newscientist.com/article.ns?id=dn4241
- Bradbury, Jane. "Human Epigenome Project -- Up and Running." PLoS Biology. Dec. 22, 2003. (Oct. 3, 2008)http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0000082&ct=1
- Brownlee, Christen. "Nurture Takes the Spotlight." Science News. June 24, 2006. (Oct. 3, 2008)http://www.thefreelibrary.com/Nurture+takes+the+spotlight:+decoding+the+environment's+role+in...-a0148858116
- "Epigenetics." Britannica Online Encyclopædia. 2008. (Oct. 3, 2008)http://www.britannica.com/EBchecked/topic/1372811/epigenetics
- The Human Epigenome Consortium. (Oct. 3, 2008)http://www.epigenome.org/
- "Human Genome Project Information." U.S. Department of Energy Office of Science. July 24, 2008. (Oct. 3, 2008)http://www.ornl.gov/sci/techresources/Human_Genome/home.shtml
- Keim, Brandon. "Whew! Your DNA Isn't Your Destiny." Wired. Aug. 16, 2005. (Oct. 3, 2008)http://www.wired.com/medtech/health/news/2005/08/68468
- "NIH Announces Funding for New Epigenomics Initiative." U.S. National Institute of Health. Sept. 29, 2008. (Oct. 8, 2008)http://www.nih.gov/news/health/sep2008/od-29.htm
- Norris, Jeffrey. "Major NIH Award Supports Epigenomics Research." UCSF Today. Oct. 2, 2008. (Oct. 8, 2008)http://pub.ucsf.edu/today/cache/feature/200810024.html
- Ray, Matt. "Epigenetics." Environmental Health Perspectives. March 2006. (Oct. 3, 2008)http://www.ehponline.org/docs/2006/114-3/toc.html
- "Silencing of the lambs." The Economist. May 10, 2008. (Oct. 3, 2008)http://www.economist.com/science/displaystory.cfm?story_id=11326195
- Wade, Nicholas. "Explaining Differences in Twins." The New York Times. July 5, 2005. (Oct. 3, 2008)http://www.nytimes.com/2005/07/05/health/05gene.html
- Young, Emma. "Rewriting Darwin: The new non-genetic inheritance." New Scientist. July 12, 2008. (Oct. 3, 2008)http://www.science.org.au/nova/newscientist/098ns_003.htm