Picture your body: It’s a collection of cells carrying thousands of genetic mistakes accrued over a lifetime — many harmless, some bad, and at le

We are all mosaics | Knowable Magazine

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2025-01-18 14:00:08

Picture your body: It’s a collection of cells carrying thousands of genetic mistakes accrued over a lifetime — many harmless, some bad, and at least a few that may be good for you.

You began when egg and sperm met, and the DNA from your biological parents teamed up. Your first cell began copying its newly melded genome and dividing to build a body.

“That process of accumulating errors across your genome goes on throughout life,” says Phil H. Jones, a cancer biologist at the Wellcome Sanger Institute in Hinxton, England.

Scientists have long known that DNA-copying systems make the occasional blunder — that’s how cancers often start — but only in recent years has technology been sensitive enough to catalog every genetic booboo. And it’s revealed we’re riddled with errors. Every human being is a vast mosaic of cells that are mostly identical, but different here or there, from one cell or group of cells to the next.

Cellular genomes might differ by a single genetic letter in one spot, by a larger lost chromosome chunk in another. By middle age, each body cell probably has about a thousand genetic typos, estimates Michael Lodato, a molecular biologist at the University of Massachusetts Chan Medical School in Worcester.