This week, scientists reported that they had successfully edited harmful mutations out of genes in human embryos. It’s just the latest in a string of gene editing firsts facilitated by a system called Crispr-Cas9, which has enabled scientists, entrepreneurs -- even middle school students -- to snip, insert and delete genetic material with unprecedented precision and ease.

Learn about how Crispr has been used over the past few years and where scientists draw the line between feasible and implausible by completing the following statement:

Crispr could...