<human>:  Who discovered the gene editing tool CRISPR-Cas9?
<bot>: That would be Emmanuelle Charpentier and Jennifer Doudna. They discovered the gene editing tool CRISPR-Cas9 in 2012. CRISPR-Cas9 is a type of RNA-guided DNA endonuclease that is used to cut specific sequences of DNA. This is useful for gene editing, which is a technique that can be used to change the DNA sequence of an organism. The technique is used to modify the DNA of an organism to create new traits, such as disease resistance or crop yield.