Written by: D. J. Sidjanin, PhD
Medical College of Wisconsin Associate Professor, Department of Cell Biology, Neurobiology & Anatomy
What is the genome?
The genome is an organism’s complete set of DNA molecules with each of our cells containing a full copy of our genomes. The human genome is about 3 billion base pairs in length and encodes the instructions or the “blue print” for the cells to synthesize proteins by highly orchestrated and strictly regulated molecular processes. Proteins are essential cellular components required for cellular structure and function. The unique combination of proteins present in various cell types creates the astonishing diversity of our tissue and organ structure and function.
Which particular DNA sequence makes us human?
The answer to this question has come after about 15 years of intense international scientific effort, which resulted in the sequencing of the entire human genome in 2003. The available genomic information started to unlock life’s code and helped us better understand who we are. Throughout the sequencing process, there were several surprises along the way. We learned that our genomic blueprint encodes about 20,000 different proteins; a number half of what was originally believed. We learned that the portions of our genome are strikingly similar to those of other species. For instance, humans share about 85% of genome sequences with mice, and about 98% similarity with chimpanzees. We also determined that as humans, we differ from each other by approximately 0.1% of our genomes. It is that 0.1% that gives us our distinguishing features, such as height, body shape, skin, hair and eye color, as well as our talents and abilities.
How does genomics relate to health?
Unfortunately, we also learned that our individual genomic variations make us susceptible to diseases. About half of all adult Americans suffer from at least one common disorder, including heart disease, cancer, diabetes, arthritis, neurodegenerative diseases and age-related vision disorders and other serious conditions. To date great progress has been made in genomic research and how it relates to the inheritance of disease. However, we still don’t fully understand which genomic variants cause or contribute to these common diseases. While poor diet, smoking and lack of exercise may all have a role, it remains unclear how these unhealthy behaviors interact with our genomic variants to cause the disease to manifest. We have not yet figured out which combination of genomic variants and lifestyle choices will, with certainty, predict who is and who is not at a risk for certain common diseases. Consequently, today’s practice of medicine is primarily reactive, with treatment beginning only after symptoms of the disease begin. Modern medicine may save millions of lives; however in some individuals the available medications are ineffective, or worse can cause adverse reactions. The unpredictable responses to the currently available therapies, much like the disease processes themselves, are also driven by our unique genomic makeup.
Personalized Medicine and the Future of Genomic Research
Deciphering which genomic variants are disease causing has proven to be a challenging task. Large-scale genomic analyses along with highly sophisticated bioinformatics tools are required to identify clinically relevant information. However, in the near future, the rapidly advancing research in genomics will allow for the unlocking of the secrets that our individual genomes hold. The future outcomes of these efforts will identify what causes a specific disease, predict drug responses, and even identify novel therapy targets. The future of our health care will be personalized, tailored to our unique genomic makeup for diagnosis and most effective treatment options available. One of the greatest promises of the genome efforts is in the identification of at-risk individuals who might be able to counteract the onset of certain diseases by choosing healthier lifestyles. Today, we stand at the dawn of personalized medicine which without doubt is the next medical frontier.