Putting It Together: DNA Structure and Replication

Let’s expand just a bit on how the process of personalized medicine works. Within any given genome there will be small differences in the DNA sequence. All humans, for example, are 99.99% identical and only differ by 0.01%. These small differences account for many features in an individual, including how they respond to disease treatments.

Personalized Medicine in Practice

Let’s return to our examples from the beginning of the chapter:

  • Blood clot treatments: Screening the genome of a patient prior to prescribing Warfarin for blood clots allows clinicians to determine if the drug will even work and if so, to pinpoint a specific dosage.
  • Colorectal cancer treatments: In the case of colorectal cancer, the KRAS protein can be examined to determine if cetuximab will be effective. This is an important step as this drug is ineffective in about 40% of patients.
  • Breast cancer treatments: Anti-breast cancer treatments can be assessed prior to trial-and-error in a patient based on the DNA sequence of key receptors in the body.

So, should you have your genes tested? Unfortunately, the decision about whether to get a particular genetic test can be complicated.

A doctor holding a file folder of informationGetting a genetic test usually isn’t difficult. Doctors generally take a sample of body fluid or tissue, such as blood, saliva or skin, and send it to a lab. Most genetic tests used today analyze just one or a few genes, often to help diagnose disease. Newborns, for example, are routinely screened for several genetic disorders by taking a few drops of blood from their heels. When life-threatening conditions are caught early, infants can be treated right away to prevent problems.

Genetic tests are now available for about 2,500 diseases, and that number keeps growing. Your doctor might advise you to get tested for specific genetic diseases if they tend to run in your family or if you have certain symptoms.

“While there are many genetic tests, they vary as to how well they predict risk,” says Dr. Lawrence Brody, a genetic testing expert at NIH.

For some diseases, such as sickle cell anemia or cystic fibrosis, inheriting 2 copies of abnormal genes means a person will get that disease. But for other diseases and conditions, the picture is more complex. For type 2 diabetes, testing positive for some specific gene variants may help predict risk, but no better than other factors—such as obesity, high blood pressure and having a close relative with the disease.

The latest approach to personalized medicine is to get your whole genome sequenced. That’s still expensive, but the cost has dropped dramatically over the past decade and will likely continue to fall. Since your genome essentially stays the same over time, this information might one day become part of your medical record, so doctors could consult it as needed.

You can start to get a sense of your genetic risks by putting together your family’s health history. A free online tool called My Family Health Portrait from the U.S. Surgeon General can help you and your doctor spot early warning signs of conditions that run in your family.

But personalized medicine isn’t just about genes. You can learn a lot about your health risks by taking a close look at your current health and habits. Smoking, a poor diet, and lack of exercise can raise your risks for life-threatening health problems, such as heart disease and cancer. Talk to your health care provider about the steps you can take to understand and reduce your unique health risks.

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