Months after a Chinese scientist stunned the world with the announcement that he had genetically altered embryos that resulted in full-term twin girls, genetics experts and ethicists are now calling for a partial ban on the use of a gene-editing technology that can be used to make modified humans.

While researchers are asking nations to prohibit the editing of DNA in sperm, eggs, and embryos intended to produce children; other technologies such as, CRISPR, could still be used for other research or for treating disease by editing non-reproductive cells. CRISPR allows scientists to alter the genome more precisely than ever before, cutting or pasting bits of genetic code as small as individual DNA letters. It's been heralded as a way to treat diseases caused by defective genes.

"This is a crucial moment in the history of science: a new technology offers the potential to rewrite the script of human life," said Carrie Wolinetz, associate director for science policy at National Institutes of Health, and Francis Collins, who directs the agency, in a letter published alongside the proposal in the journal Nature. "Human gene editing for reproductive purposes carries very serious consequences -- social, ethical, philosophical and theological. Such great consequences deserve deep reflection."

One major concern is the ease in which the technology can potentially be misused. There are also fears that someone could modify genes in a way that could potentially harm patients, or possibly cause an abnormality, which could become an inherited trait that would be passed down generation to generation. The potential slowdown in experimental progress is worth stopping misuse, the researchers said.

"The framework we are calling for will place major speed bumps in front of the most adventurous plans to re-engineer the human species," wrote the researchers. "But the risks of the alternative -which include harming patients and eroding public trust -are much worse."

Jennifer Doudna, credited as an inventor of CRISPR and professor of biochemistry and molecular biology at the University of California, Berkeley, states that a call for prohibition is too little, too late. She and other researchers called for a ban years ago.

"We had guidelines, but we didn't have any kind of articulated consequences," she said in a telephone interview. "The world needs to figure out how to put into place very strict requirements with appropriate consequences that make it unthinkable to violate them."

That is just what is happening to He Jiankui, the geneticist, who genetically altered the embryos of the twin girls in China. Because of his work, he is now in state detention and could possibly be facing the death penalty if convicted.