Scientists may now be close to understanding how germ cells are assigned to become sperm cells or egg cells after a team of Japanese researchers have identified a "genetic switch" in a type of small fish called the medaka.

For the study, researcher Toshiya Nishimura and his colleagues conducted experiments and examined medaka, which is also known as Japanese rice fish, Financial Express has learned.

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Apparently, the minute fish has this gene called foxI3, which actually serves as a switch that controls which germ cells are bound to turn into eggs and which ones are to become sperm cells.

Nishimura and his group noticed that the foxI3 gene is expressed in germ cells alone; the gene is not present in the surrounding cells of the medaka's reproductive organs.

Thus, the group of scientists noted that the foxI3 serves as the "genetic switch" that provides the molecular signal in preventing sperm formation. That said, foxI3 is only active in the female germ cells.

While it's already an established fact that germ cells develop into either sperm or egg, the mechanism that determines which germ cells turn into egg or sperm remains to be elusive, according to NYC Today.

"This sexual switch that is present in the germ cells is independent of the body's sex is an entirely new finding," Nishimura said.

To further justify that fixI3 acts as a genetic switch, Nishimura and his team inactivated the gene in adult fish with XX chromosomes and found out that sperm cells were formed in the female reproductive organ of the fish.

The sperm cells formed in the experiment were notably functional and were capable of fertilizing egg cells. 

Although the findings of the research can help identify the mechanism that determines which germ cells develop into sperm or egg, scientists are still faced with a different challenge since humans do not have the foxI3 gene.

Another study author, reproductive biologist Minoru Tanaka of Japan's National Institute for Basic Biology, admitted that there are still no established clues on whether vertebrates germ cells also have the same "genetic switch" mechanism, Reuters reports. 

"The germ cells were regarded as passive cells that are regulated by other cells," Tanaka added. 

The revolutionary study was published in the journal Science on Thursday.

TagsGenetics, Study, Germ Cells, Science