A TIMELINE OF GENETIC MODIFICATION

1971–73

Development of recombinant DNA allows researchers to cut and paste genes in bacteria.

1978

A team at Genentech adds the human insulin gene to bacteria, launching the biotechnology industry.

1990

Doctors in Pennsylvania attempt gene therapy on a four-year- old girl. A gene is added to her body using a virus.

1999

Teenager Jesse Gelsinger is the first person to die in a genetherapy experiment. Commercial interest slows dramatically.

2009

US biotechnology firm Sangamo Biosciences initiates an effort to cure HIV with blood cells from which it has, for the first time, deleted a human gene.

2013

Scientists in the US and South Korea demonstrate CRISPR as a new, much easier method of changing human genes. Editas Medicine is founded in Boston to develop CRISPR treatments.

2014

Adding CRISPR to muscle cells in a lab dish, a team at Duke University eliminates a mutation that causes Duchenne muscular dystrophy.

2015

Chinese scientists edit the DNA of human embryos. Within months, the world’s scientists condemn as “irresponsible” any attempt to make gene- edited babies.

2016

First human tests of CRISPR, as part of cancer treatments, win initial approval in the US and China.