The scientists, led by Zhang Yonglian with the Shanghai Research Institute of Life Sciences, and Chen Xiaozhang with the Chinese University of Hong Kong, have identified and replicated the gene, named Bin1b, which is responsible for the maturation of sperm.

Zhang said their discovery implies that men must have a gene with the same function.

"If our assumption proves correct, we should be able to create some new contraceptive drugs for men," Zhang said.

According to Zhang, the gene, discovered in the rat's epididymis, a long narrow tube in the male reproductive system, functions to provide a "secure environment" against bacteria as the sperm develops.

By disabling the gene temporarily, Zhang said, it is possible to hinder the maturation of sperm and thus control birth.

Zhang said that most of the current contraceptive means are targeted at women and that there is no safe and effective birth-control drug for men.

Since the rat gene appears to have one single function, drugs regulating it should have low health risks, Zhang added.

The scientists published their findings in the latest issue of the Science magazine. They are now concentrating on probing the key to regulating the gene.