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Genes and Identity

It is starkly evident that our lives and persona are the result of both genetic and environmental influences. When the human genome was sequenced a decade ago it stirred hope that knowing the chemical identity of our own personal DNA would yield precise clues about what to expect in our lives. Even though the genome can’t anticipate what environmental factors might be present, knowledge about it was expected to predict the likelihood for particular diseases. There are even commercial companies who sell analyses of an individual person’s DNA.

Alas, DNA predictions are not that easy, at least according to a recent investigation by Johns Hopkins and Harvard researchers. The study is a massive screening of disease outcomes for 24 different maladies in over 50,000 sets of identical twins. The pairs start life with matching genes so they have the same genetic risk factors, but different environmental experiences as their lives unfold.

For most individuals the sequence results are neither negative nor positive predictors—the subject can’t tell if they have an increased or decreased risk for a particular disease by knowing about their DNA composition. There is a small subset of diseases (type 1 diabetes and Alzheimer’s, for example) where knowledge of DNA sequence can give an indication, though not an absolute determination, of potential trouble in a person’s future.

These results, while disappointing to DNA sequencing boosters, are probably not surprising. Most human pathologies are underlain by multiple genetic changes so simple associations of risk and mutations are relatively rare. Moreover, the best genetic variations can do is to predict probabilities: e.g., if you have this particular mutation you are 17% more likely to get colon cancer. This is precisely the opposite of traditional ideas of personalized medicine, which should deal with an individual, not a statistical probability based on a population-wide study.

Apparently, we have a long road ahead before the full flowering of the DNA age takes hold to make for a healthier and more predictable life.

Related:
Discount DNA [Periodic Tabloid]
Your Genome [Distillations]
Study Says DNA's Power to Predict Illness is Limited [New York Times]

Posted In: Technology

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