(CNN) – A newer, more precise form of CRISPR, known as base editing, can change a single letter (or base) of DNA at a time.

Base editing was used for the first time in a 2022 clinical trial to modify the immune cells of a UK teenager after doctors exhausted all other options to treat her form of leukemia. Eight other children and two adults have gone on to receive the treatment. And last year, doctors used base editing to treat a baby born with a severe CPS1 deficiency, a rare and dangerous genetic disease.

Now, two new studies have used the technique to edit human embryos in the earliest stages of development, donated for research purposes by individuals who underwent IVF treatment. Both teams found that the precision of the technique reduced the likelihood of unintended chromosomal abnormalities. (Read More)