Your genes affect not only how you look and your predisposition to disease, but it would appear that they also affect your responsiveness to different drug treatments following disease onset.

In the emerging field of pharmacogenetics, scientists study genome variations and correlate them with drug treatment response.  For example, variations (also called polymorphisms) in genes encoding enzymes involved in drug metabolism have been found to affect the activation, deactivation, and toxicity of drugs used to treat cancer, heart disease, and psychiatric disorders.  Recently, scientists found that DNA sequence can also be used to predict responsiveness to current Hepatitis C treatment (a 48-week course of peginterferon-α-2b combined with ribavarin).

The sequence at a single DNA position (single nucleotide polymorphism, or SNP) on chromosome 19, close to the gene encoding the interferon-λ-3 protein, has a significant effect on a patient’s ability to clear Hepatitis C infection with treatment.  Patients with a C nucleotide at the critical position on both copies of chromosome 19 (CC genotype) are two to three times more likely to respond to treatment than those patients with the T nucleotide at the same position (TT genotype).

In the case of Hepatitis C, the mechanism by which one sequence is more therapeutic than the other is not yet understood.  However, sequence information can still assist doctors in selecting appropriate treatments: as alternative Hepatitis C treatments become available, doctors may bypass the current treatment for those patients with the TT genotype.

As DNA sequencing becomes cheaper and easier, and genome information becomes elucidated, the personalization of medicine may become a reality.