A pair of buff beagles may have the edge in doggy body-building contests. Scientists in China changed the dogs’ genes to make the small hounds extra-muscular.
The dogs are the latest addition to a menagerie of animals — including pigs and monkeys — whose genes have been “edited” by scientists. The pups’ genes were altered with a powerful technology called CRISPR/Cas9.
Cas9 is an enzyme that cuts through DNA. CRISPRs are small pieces of RNA, a chemical cousin of DNA. The RNAs guide the Cas9 scissors to a specific spot on DNA. The enzyme then snips the DNA at that spot. Wherever Cas9 cuts the DNA, its host cell will try to repair the breach. It will either paste the cut ends together or copy unbroken DNA from another gene and then splice in this replacement piece.
Tying together broken ends can result in mistakes that disable a gene. But in the dog study, those so-called mistakes were actually what the Chinese scientists had been aiming for.
