Discovery Of Genetic Switch Which Determines Sperm Or Egg

Researchers have found the mystery behind the genetic switch which determines whether the germ cell will become became sperm or eggs.

By studying a small fish called Medaka a gene named foxl3 has been identified.  This gene works in the germs cells of females to suppress differentiation into sperm.

The females who lacked this gene however still looked exactly similar to the other small female fish, however a large number of sperm are formed in the ovaries, and a small number of eggs are formed at the same time.

Dr Toshiya Nishimura, Associate Professor Minoru Tanaka from the National Institute for Basic Biology, National Institutes of Natural Sciences in Japan and colleagues found it surprising that despite the environment surrounding the germ cells being female, functional sperm has been made.

Dr. Nishimura stated that this is a completely new finding that the sexual switch present in the germ cells is not dependent on the body’s sex. “While germ cells can become either sperm or eggs, nobody knew that in vertebrates the germ cells have a switch mechanism to decide their own sperm or egg fate,” Tanaka said.

“Our result indicates that once the decision is made the germ cells have the ability to go all the way to the end. I believe it is of very large significance that this mechanism has been found,” Tanaka said.

This research will be published in the journal Science.


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