PHOENIX - A law signed Friday by Gov. Jan Brewer makes it a crime to create or attempt to create a human embryo other than by means of fertilization of a human egg with a human sperm.

The law, which takes effect July 29, even more specifically bars anyone from intentionally or knowingly creating or attempting to create a human-animal hybrid.

Rep. Nancy Barto, R-Phoenix, who wrote the measure, said there's no evidence such research is going on in Arizona or any other state. But she noted that scientists in the United Kingdom reported putting human DNA into empty cow eggs.

None of that is producing anything like a living being that is half-human, half-bull. The scientists stated they wanted to create special embryonic stem cells for research into disease.

Barto, however, said even that goes too far, which is why the state needs laws against the practice.

"It's placing some ethical boundaries around scientific research in Arizona," she said. Barto said this law will "proactively" prevent such experimentation.

Barto rejected the idea this type of broad ban would stymie legitimate medical research. "We're drawing a protective line to say that human life is valuable and needs to be protected," she said. "We need to make sure that we're not going outside of that ethical boundary."

Barto said even if there were some legitimate need to create human-animal stem cells, which she doesn't believe there is, there is no evidence that's where the research would stop.

"It's going to be up to somebody to decide how much 'human' is a new creation, whether or not they're going to deserve rights," she said. "It's important that somebody makes a distinction before we have some mad scientist doing that kind of thing."

The new law goes beyond just mixing DNA. It also bars putting a human embryo into a non-human womb, or vice versa. And it bans the sale of laboratory-created human embryos except for the treatment of infertility.

A related bill signed Friday by Brewer puts new restrictions on the ability of a woman to sell her eggs for purposes other than fertility treatments. And it requires would-be egg donors to be informed of potential risks.