Monday, October 13, 2014

The Giant Mutations in the Human Genome


Our genomes are a mess—and we’re only beginning to understand the societal costs behind such genetic uncertainty.

Intellectual disability and developmental delay disorders are surprisingly common, but they’re frustratingly mysterious and hard to categorize. Patients often show a baffling mix of symptoms that are sometimes subtle and sometimes severe. Why are developmental disorders so confusing?

It turns out that there is a class of giant DNA mutations that share features of developmental disorders: They are surprisingly common, frustratingly diverse, and hard to categorize. Researchers are now discovering that these mutations play a big role in developmental delay disorders. The baffling symptoms are a consequence of the underlying genetic turmoil.

Despite the tremendous amount of quality control machinery in the cell devoted to making accurate copies of our DNA, our genomes are surprisingly unstable. Mistakes are made, and not just small typos: Entire paragraphs and pages of our genetic text get duplicated or deleted. These large mutations are called “copy number variants” or CNVs, and they add or subtract copies of genes.
Finding these mutations is only the beginning. Understanding why they cause particular effects is the next challenge.
Over the past decade, scientists have discovered CNVs to be shockingly common. One study found that we each carry, on average, about 1,000 CNVs, affecting roughly three percent of our genes. Different individuals have different CNVs, and so across the entire human population, much of the human genome is affected by these radical alterations.

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