In a first, human embryos edited to explore gene function
CRISPR/Cas9 is used to ‘knock out’ a gene needed to develop properly
EMBRYO, INTERRUPTED A 5-day-old human embryo is usually composed of about 200 cells in a hollow ball configuration called a blastocyst (left). Embryos edited to remove the OCT4 gene (right) fail to make normal blastocysts.
K. Niakan/Nature 2017