Some serve as backups for damage to our genetic code, while others are common in cancer mutations. With CRISPR, a group of enzymes recognize certain repeats, and break the DNA there to insert important information in the middle. These insertions are called “spacers,” and they contain the genetic code of different viruses that have invaded in the past. Using CRISPR on babies is widely illegal. But there are some cases where using CRISPR on humans may be worth the risk.