Rewriting genes, that couldn’t go wrong!
There’s a fairly simple alphabet that spells out the directions for what genes want the body’s cells to do. But sometimes there’s a mistake — essentially a typo — in those directions. Now, working somewhat like a pencil, new tools can edit the body’s genes one letter at a time. They can fix about half of the simple typos that cause human diseases.
The new tools are based on a technology called CRISPR/Cas9. It’s like a set of molecular scissors that snips DNA. Scientists can guide the scissors to the exact spot in an organism’s genetic instruction book where they want to cut something out. They’ve used the tool to make faulty genes — mutations — or correct them. And they’ve done this in animals and in human cells.
Scientists also have ways to use CRISPR/Cas9 to change gene instructions without cutting DNA at all. These tools are called “base editors.” A DNA base is a molecule represented by a single letter in the body’s genetic code. There are four DNA bases, known as A, C, T and G.
Base editors can fix one-letter typos in the genetic code. So far, they’ve only been able to fix one type of error: They’ve turned C’s into T’s.
Using these tools, scientists have changed genes in plants, fish, mice — even in human embryos.