In a world first, scientists at Bar-Ilan University say they have discovered that a single-letter switch in a region of the genome once dismissed as “junk DNA” can reverse the biological sex of a mouse.

“If you change just one letter in the DNA in a place that doesn’t create proteins, and does not encode for anything, you can prevent the ability to create an ovary, and instead you will get development of testes,” said principal investigator Dr. Nitzan Gonen from the Mina and Everard Goodman Faculty of Life Sciences and Institute of Nanotechnology and Advanced Materials, in a recent video call with The Times of Israel. “This is why it’s super exciting.”

Using CRISPR technology, a gene-editing tool, the scientists changed “just one DNA letter out of about 2.8 billion,” Gonen said. “I was completely surprised to find that XX mice, which genetically should have been female, developed instead as males with full testes and male genitalia.”

The scientist said that 98 percent of our DNA, which is known as “dark matter” because it does not code for proteins, may hold the key to understanding mutations.

“Non-coding DNA can have a profound effect on development and disease,” Gonen said.

The peer-reviewed research, headed up by doctoral student and lead author Elisheva Abberbock and other researchers from Bar-Ilan University, along with Dr. Ariel Afek of the Weizmann Institute and Dr. Francis Poulat of the University of Montpellier, was published on Thursday in Nature Communications.

Biological sex, gender, and sexual orientation

Gonen laid the groundwork of her research by saying that when people talk about sex, “many people have the tendency to confuse biological sex with gender and with sexual orientation, but those are actually three different pillars or layers.”

Sex determination is a process that is “fully biological,” and it “all happens during embryonic development, giving rise to males or females.”

“We understand much of it, but not all of it,” she said.

The next issue is gender, she said, which may have a biological trait, “but we don’t have really good tools to study that with mice.”

“No........

© The Times of Israel