The Streptococcus pyogenes Cas9 endonuclease can be targeted to a specific genomic DNA sequence by an sgRNA that at its 5′ end has 20 nucleotides complementary to the target sequence. If this target sequence is immediately upstream of the protospacer adjacent motif (PAM) 5′NGG-3′, Cas9 will cleave the target DNA. Suppose you have chosen a 20-nucleotide target sequence in the genome of Drosophila melanogaster and that this sequence is next to the required PAM. How could you determine if Cas9 will cleave only this sequence in the Drosophila genome?