How Many Genes Does a Body Need?

Only about 15 percent of the human genome or 3,230 genes—that we know of

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Humans have about 19,000 genesmore than a chicken, but less than an onion. But which genes are mandatory for human life? Elizabeth Pennisi reports for Science that the number is surprisingly small: a mere 3,230, or around 15 percent of the human genome.

The number was reported in a recent study just pre-printed by bioRxiv. Researchers aggregated protein-coding region sequence data, or exomes, for 60,706 diverse individuals, then compared the information. This massive number of individuals is about ten times larger than any other similar project, reports Pennisi.

The results show a whopping ten million variants within the genes. And when the team compared the number of variants to the number that would have arisen if the changes occurred by chance, they found 3,230 genes with no variants.

“Such data,” writes Pennisi, “suggests that, whenever one of these genes mutates, the embryo usually dies or the person is too sick to reproduce.” Hence, those genes are considered essential to the body, which just can’t live or reproduce without them.

The team admits that their analysis has its faults: In the study, they write that their sample size was large, but probably not big enough to identify all of the essential genes in the body. More analysis is also needed not only to understand what the “essential genes” control in the body, but to figure out how they’re connected to medical conditions.

But it’s a start—and they’re making their huge database publicly available to encourage other scientists to see what it yields.

In the meantime, 3,230 seems like the minimum number of genes people simply can’t get along without, which (for now) beats many of our fellow organisms. But who knows what a comparison of onion genes might reveal?

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