Figure 9.

Schematic representation of a CRISPR molecule bound to bacterial chromosomal DNA. For simplicity of presentation, the Cas9 protein molecule is not shown. The CRISPR molecule is positioned opposite the target sequence on the chromosomal DNA by the (80–100 nucleotide long) sg DNA shown in red. A single or a multiple (i.e., large) nucleotide deletion in the middle of a gene yields a knockout mutation that no longer encodes the product of that gene. An altered or changed nucleotide generally yields a missense mutation that encodes an altered version of the original protein. A large nucleotide insertion may be used to introduce an entire gene.