The Story in Your Genes

The Story in Your Genes

There's tremendous value in genetic data, but it depends on how deeply you look:

1 Each person's genome consists of 3 billion pairs of DNA molecules twined into the long double helix that forms our 46 chromosomes. Those paired bits of DNA come in four types, represented by A, C, T, and G, which form our genes.

2 Most of the billions of letters are the same in every person. But they differ at perhaps 10 million places. You might have a "T" at one location, while someone else has a "C." These differences are called SNPs, for single nucleotide polymorphisms.

3 Mutations in genes cause certain diseases, such as cystic fibrosis and sickle cell anemia. In contrast, SNPs usually are only weakly linked to the risk of diseases, studies show. And so far, the personal genomics companies analyze only SNPs.

4 Among other problems, today's gene testing covers only a small fraction of SNPs. But even if all SNPs were tested, is it really medically useful to know that your SNPs are associated with, say, a 5% higher risk of multiple sclerosis?

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