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A New Gene Editing Tool Could Rival CRISPR, and Makes Millions of Edits at Once

First discovered in 1984, retrons are floating ribbons of DNA in some bacteria cells that can be converted into a specific type of DNA—a single chain of DNA bases dubbed ssDNAs (yup, it’s weird). But that’s fantastic news for gene editing, because our cells’ double-stranded DNA sequences become impressionable single chains when they divide. Perfect timing for a retron bait-and-switch.

Normally, our DNA exists in double helices that are tightly wrapped into 23 bundles, called chromosomes. Each chromosome bundle comes in two copies, and when a cell divides, the copies separate to duplicate themselves. During this time, the two copies sometimes swap genes in a process called recombination. This is when retrons can sneak in, inserting their ssDNA progeny into the dividing cell instead. If they carry new tricks—say, allowing a bacteria cell to become resistant against drugs—and successfully insert themselves, then the cell’s progeny will inherit that trait.

Because of the cell’s natural machinery, retrons can infiltrate a genome without cutting it. And they can do it in millions of dividing cells at the same time.