In 2003, after more than a decade of research, the Human Genome Project was completed by the U.S. Department of Energy and the National Institutes of Health.
The goals of the Human Genome Project were to learn the order of the 3 billion units of DNA that go into making a human genome, as well as to identify all of the genes located in this vast amount of data. By 2003, almost all of the pairs of chemicals that make up the units had been put in the correct sequence—enough for a pronouncement of success. The individual genes within the long strands of DNA, and the elements that control the genes, are still in the process of being identified. Current counts indicate that the human genome contains 22,000 to 23,000 genes.
One of the early hopes of the genomic project was to pinpoint specific genes that caused common diseases. Scientists now think the answer is more complex, with many diseases the result of multiple genes interacting. Nevertheless, the information garnered from the genome project has the potential to forever transform healthcare. Many believe that genome-based medicine, frequently called personalized medicine, is the future of healthcare—the next logical step in a world in which more is known about human genetics, disease, and wellness than ever before.
Of all the scientific and social promises that stem from advances in our understanding of the human genome, genomic medicine may be the most eagerly awaited. The prospect of examining a person's entire genome, or at least a large portion of it, in order to make individualized risk predictions and treatment decisions is tantalizingly within reach.
This discussion will explain the genomic basis of personalized medicine and explore its potential for good as well as its possible risks.
- What is the human genome?
- What is personalized medicine?
- Is personalized medicine only for sick people?
- How might I get my genomic profile or learn my predisposition for certain medical conditions? What things should I consider before doing so?
- Where can I look for more information about personalized medicine and genome science?
The human genome is the blueprint for each person's body, influencing how we look, our genetic predispositions for certain medical conditions, how well our bodies fight disease or metabolize food, and which therapies our bodies do and do not respond to.
The genome consists of an organism's total DNA, including its genes. DNA—the famous "double helix"—is composed of four chemicals, which are repeated many times in different sequences. (The names of the chemicals are abbreviated as A, T, C, and G. That's why DNA is sometimes referred to as a code with a four-letter alphabet.) The sequence of the chemicals dictates the type of organism that develops, as well as other critical life functions. The human genome contains approximately 3 billion pairs of these chemicals.
Genes are believed to make up only about 2 percent of the human genome, with the rest consisting of "noncoding" regions, thought to regulate the function of genes and contribute to the structural integrity of chromosomes.
Personalized medicine is a young but rapidly advancing field of healthcare that is informed by each person's unique clinical, genetic, genomic, and environmental information. Because these factors are different for every person, the nature of diseases—including their onset, their course, and how they might respond to drugs or other interventions—is as individual as the people who have them.
Personalized medicine is about making the treatment as individualized as the disease. It involves identifying genetic, genomic, and clinical information that allows accurate predictions to be made about a person's susceptibility of developing disease, the course of disease, and its response to treatment.
In order for personalized medicine to be used effectively by healthcare providers and their patients, these findings must be translated into precise diagnostic tests and targeted therapies. This has begun to happen in certain areas, such as testing patients genetically to determine their likelihood of having a serious adverse reaction to various cancer drugs.
Because the 2003 sequencing of the human genome provided crucial insight into the biological workings behind countless medical conditions, scientists and physicians are advancing the field of personalized medicine at a fast pace. It is not yet an established part of clinical practice, but a number of top-tier medical institutions now have personalized medicine programs, and many are actively conducting both basic research and clinical studies in genomic medicine.
Specific advantages that personalized medicine may offer patients and clinicians include:
- Ability to make more informed medical decisions
- Higher probability of desired outcomes thanks to better-targeted therapies
- Reduced probability of negative side effects
- Focus on prevention and prediction of disease rather than reaction to it
- Earlier disease intervention than has been possible in the past
- Reduced healthcare costs
Personalized medicine is not to be confused with "genetic medicine." Genetics, a field more than 50 years old, is the study of heredity. It examines individual genes and their effects as they relate to biology and medicine. "Single cell" genetic diseases include muscular dystrophy, cystic fibrosis, and sickle cell anemia. (However, even these seemingly "simple" hereditary disorders can be influenced by other genes, as well as by environmental factors such as diet and exposure to toxins.)
Genomic and personalized medicine aims to tackle more complex diseases, such as cancer, heart disease, and diabetes, for years believed to be influenced primarily by environmental factors and their interaction with the human genome. It is now understood that because these diseases have strong multigene components—and in some cases might be caused by errors in the DNA between genes instead of within genes—they can be better understood using a whole-genome approach.
Definitely not. Because an individual's genome influences his or her likelihood of developing (or not developing) a broad range of medical conditions, personalized medicine focuses strongly on wellness and disease prevention.
For example, if a person's genomic information indicates a higher-than-average risk of developing diabetes or a particular form of cancer, that person may choose a lifestyle, or sometimes be prescribed medications, to better regulate the aspects of health and wellness over which he or she has control. The person may benefit in the long run from making preventive lifestyle choices that will help counteract the biological risk.
Genomic medicine may help determine a person's risk of developing several specific medical conditions, including:
- Cardiovascular disease
- Neurodegenerative diseases
- Neuropsychiatric disorders
Researchers are actively investigating the genomic and genetic mechanisms behind—and developing predictive testing for—such diverse medical conditions as:
- Infectious diseases, from HIV/AIDS to the common cold
- Ovarian cancer
- Cardiovascular disease
- Metabolic abnormalities
- Neuropsychiatric conditions, such as epilepsy
- Adverse drug reactions
- Environmental exposure to toxins
4. How might I get my genome profile or learn my predisposition for certain medical conditions? What things should I consider before doing so?
If you are interested in learning about your genome profile or your genetic risk for specific medical conditions, start by speaking with your physician. Other resources include genetic counselors and reputable medical centers with genome science or personalized medicine programs.
In addition, a number of companies that test the DNA of paying consumers—such as deCode Genetics, 23andMe, and Navigenics—are being launched around the world. However, caution is advised in using these services. While some states now regulate direct-to-consumer genetic tests, regulation is not yet standardized. Experts recommend that consumers seek interpretation of test results from a professional who specializes in this type of testing.
Even on-site at your doctor's office, genetic analysis or genome profiling can raise a number of questions relating to ethics, privacy, quality of life, and whether or not findings currently have any real clinical value.
While some people may not wish to know their genetic risk for some conditions—such as their chances for developing a devastating and untreatable condition such as Alzheimer's disease—others may find such information has personal utility. For instance, they may use the knowledge they gain to plan for the future. Our DNA can provide other insights, as well, such as who our ancestors were.
The Genetic Information Non-Discrimination Act of 2008 (GINA) prohibits the use of genetic/genomic information by health insurance companies for determining a person’s eligibility for insurance or determining insurance premiums—as well as by employers for making decisions about functions such as hiring and firing, assigning jobs, and promoting and demoting. Because consumers should now be able to obtain their genome profiles and other genetic information without fear of retribution, GINA is reinvigorating the field of genomic testing.
Both medical providers and members of the public must better understand these important topics before widespread genetic testing is conducted and made a standard of medical practice. As familiarity with genetic and genomic testing grows, experts will need to carefully assess its utility for patient care to make informed decisions about how to best integrate them into medical practice.
There are a number of valuable online resources about genome science and its implications for personalized medicine, with definitions, illustrations, statistics, and frequently asked questions. Those resources include:
- About the Human Genome Project
- Age of Personalized Medicine
- Duke Institute for Genome Sciences and Policy
- Duke Personalized Medicine Web site
- Genetics and Genomics for Patients and the Public (National Human Genome Research Institute)
- National Office of Public Health Genomics (Center for Disease Control and Prevention)
Last reviewed on 1/20/11
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