Designer genes now a reality

Two beagle puppies called Tiangou and Hercules were created to be extra muscular by deleting a single gene called myostatin. Photo / Supplied

You've heard of designer babies in science fiction, but it's getting closer to reality: scientists in China claim they are the first to use gene editing to create "designer dogs" with special characteristics.

Two beagle puppies called Tiangou and Hercules (pictured below) were created to be extra muscular - with double the amount of muscle mass than usual - by deleting a single gene called myostatin.

The team from the Guangzhou Institutes of Biomedicine and Health reported their results last week in the Journal of Molecular Cell Biology, saying the goal was to create dogs with other DNA mutations, including ones that mimic human diseases such as Parkinson's and muscular dystrophy, so human treatments could be tested on them.

The muscle-enhanced beagles were created using a gene-editing technology called Crispr-Cas 9 - a sort of cut-and-paste tool for DNA that allows you to design living creatures the way you want on a computer, and then create them.

"It's one of the most precise and efficient ways we have of editing DNA in any cell, including humans," said Professor George Church of Harvard University, who is a pioneer in the field of genetic engineering.

Since the technique is relatively simple, there are valid fears that humans could be next.

The flames were fanned in April when another Chinese team reported altering human embryos in the laboratory in an attempt to correct a genetic defect that causes beta-thalassemia disease.

"We have already modified embryos of both pigs and primates," Professor Church said. "It might actually be safer, and developmentally important, to make corrections in a sperm or embryo rather than a young child or an adult."

For instance, he said, gene editing can be used to correct some forms of blindness, but it has to be done on babies, or young children, before their neurons become solidified and more resistant to change.