<p><strong>Deoxyribonucleic acid (DNA) is the chemical compound</strong> that contains the instructions needed to develop and direct the activities of nearly all living organisms. DNA molecules are made of two twisting, paired strands, often referred to as a double helix.</p>

<p>Each DNA strand is made of four chemical units, called nucleotide bases, which comprise the genetic &quot;alphabet.&quot; The bases are adenine (A), thymine (T), guanine (G), and cytosine (C). Bases on opposite strands pair specifically: an A always pairs with a T; a C always pairs with a G. The order of the As, Ts, Cs, and Gs determines the meaning of the information encoded in that part of the DNA molecule just as the order of letters determines the meaning of a word.</p>

<p>The International HapMap Project, in which NIH also played a leading role, represents a major step in that direction. In October 2005, the project published a comprehensive map of human genetic variation that is already speeding the search for genes involved in common, complex diseases, such as heart disease, diabetes, blindness, and cancer.</p>

<p>Another initiative that builds upon the tools and technologies created by the Human Genome Project is The Cancer Genome Atlas pilot project. This three-year pilot, which was launched in December 2005, will develop and test strategies for a comprehensive exploration of the universe of genetic factors involved in cancer.</p>

<p>With the vast trove of data about human DNA generated by the Human Genome Project and the HapMap Project, scientists and clinicians have much more powerful tools to study the role that genetic factors play in much more complex diseases, such as cancer, diabetes, and cardiovascular disease that constitute the majority of health problems in the United States. Genome-based research is already enabling medical researchers to develop more effective diagnostic tools, to better understand the health needs of people based on their individual genetic make-ups, and to design new treatments for disease. Thus, the role of genetics in health care is starting to change profoundly and the first examples of the era of personalized medicine are on the horizon.</p>

<p>It is important to realize, however, that it often takes considerable time, effort, and funding to move discoveries from the scientific laboratory into the medical clinic. Most new drugs based on genome-based research are estimated to be at least 10 to 15 years away. According to biotechnology experts, it usually takes more than a decade for a company to conduct the kinds of clinical studies needed to receive approval from the Food and Drug Administration.</p>

<p>Screening and diagnostic tests, however, are expected to arrive more quickly. Rapid progress is also anticipated in the emerging field of pharmacogenomics, which involves using information about a patient's genetic make-up to better tailor drug therapy to their individual needs.</p>

<p>Clearly, genetics remains just one of several factors that contribute to people's risk of developing most common diseases. Diet, lifestyle, and environmental exposures also come into play for many conditions, including many types of cancer. Still, a deeper understanding of genetics will shed light on more than just hereditary risks by revealing the basic components of cells and, ultimately, explaining how all the various elements work together to affect the human body in both health and disease.</p>