March 19, 2009

UNIT 3: GeneticsMedical Technology — The Genetic Forefront

A college student comes down with the flu. Worried about missing class, he goes to an emergency clinic and is given a prescription for an antiviral flu drug. Thirty minutes after taking the first pill, he is gasping for breath and his heart is racing. He is rushed to the hospital, where doctors tell him he has had an adverse reaction to his antiviral medication.

A Cure Worse than the Disease

Usually, medications cause only mild side effects, such as drowsiness, headaches, or nausea. Occasionally, patients are allergic to medicines and break out in hives or go into shock. But sometimes reactions to drugs are more serious. In the United States, about 2.2 million patients per year are hospitalized because of adverse drug reactions, and 100,000 die. Of course, no doctor intends for a drug’s side effects to be worse than the disease it is meant to cure. Nonetheless, the current process of prescribing drugs based on medical and family history is one of trial and error.

Customized Drugs

An emerging field called pharmacogenomics is about to revolutionize the prescription process. Pharmacogenomics is the study of how genetic variations can cause different people to react in different ways to the same drugs. In most cases, for example, genetics determines the way in which—and the speed at which—a person’s body breaks down a medication. If a person’s body metabolizes a drug too quickly, the drug may not be effective. If the drug is metabolized too slowly, a standard dose may be too much.

In the future, a patient in need of a prescription could have a blood test, and health care workers could run the blood test results through a computer using biochip, or microarray, technology. In hours, a patient’s doctor could have enough information about the person’s genetic background to predict how the patient would respond to a certain drug and decide whether the dose should be changed. Individuals may even be able to have their genomes mapped and put onto cards that they can take to every doctor visit. Biochip technology is not yet available in most doctors’ offices, but some oncologists (cancer specialists) are already screening patients for particular genotypes before prescribing medications.

Gene Therapy

While pharmacogenomics can provide doctors with more information about their patients, gene therapy may someday provide them with another tool. Some diseases, such as Alzheimer’s disease and hemophilia, have a strong genetic basis. Researchers hope to replace disease-causing alleles with normal ones.

The field of gene therapy is developing slowly because it requires researchers to accomplish several feats. First, they must alter an existing virus—or some other agent that can carry genetic material—so it no longer causes disease; then they insert normal human DNA into it. Next, they must test this virus to make sure that it is safe for humans. Finally, they must test the therapy itself, to see if the virus can carry human DNA to the cells that need it. Much of this research is still being done in animals, but there have been a few successful gene therapy trials in humans.

Other Uses

New uses for DNA technology offer both solutions and hard choices. Some of the more difficult questions involve the following kinds of projects:

• Researchers can alter the DNA of viruses to make them harmless and then use the harmless version of the virus as a vaccine.
• Scientists are developing transgenic animals that can be used as medical supply factories. For example, researchers hope to breed pigs that have organs that could be used for human transplants.
• Researchers are engineering crops that contain vaccines that could be administered orally. These vaccines would be easier to grow and distribute in developing countries than are current vaccines.

Unanswered Questions

The Human Genome Project has generated a lot of excitement about its potential use for pharmacogenomic applications. However, many challenges must be addressed before pharmacogenomics can have widespread clinical application.

• Many of the current studies of patients’ responses to different drugs have conflicting results, probably due to small sample sizes, different criteria for measuring a good response, and different population groups.
• Patients’ responses to a drug may be caused by many genes. Scientists will need to study the effect of multiple genes to determine response.
• Genotype testing may increase short-term healthcare costs, which raises questions about who will pay and who will have access to the technology.

UPDATES: Straight from the Headlines

• Frankenfoods or Good Nutrition? GMOs Created but Not Regulated
• Controlling Parkinson’s with Gene Therapy
• Gene Mutations Linked to Spontaneous Cases of Schizophrenia
• Discovery and Use of Glowing Protein Leads to Nobel Prize for Three Scientists
• “Astronaut Food Approach” to Medical Testing
• Vaccines Delivered By A Smoothie

Last updated March 19, 2009 | Comments (8) | Permalink | UNIT 3: Genetics