A government research panel specializing in life ethics approved the modification of genes from fertilized human eggs for basic research to treat genetic diseases.

As of now, however, the panel will not allow births with gene-modified fertilized eggs due to safety and ethical considerations.

The panel's decision will pave the way for research that could start in spring next year at the earliest into ways to correct genetic defects.

Genome editing to repair gene abnormalities in fertilized eggs is aimed at preventing genetic defects from being passed down through generations.

There are more than 5,000 genetic diseases whose causal genes are already known. But there are fears that current genome editing technologies could alter healthy genes while defective ones are being repaired.

Questions have also been raised about the possibility of new health issues emerging if a mistake is made in the gene editing process, resulting in genetic damage being passed to offspring.

The panel has not permitted fertilized eggs, whose genes have been manipulated, to be transplanted into the womb.

At least 12 cases are known in the United States, China and elsewhere, where genome editing was done on fertilized eggs. In about half of the cases, the intention was to prevent intractable and other diseases.

"People will welcome genome editing of fertilized eggs if it prevents genetic diseases," said an expert who took part in the research panel's discussions. “Basic research must be carried out. Otherwise, there is little possibility of being able to alter genes with total accuracy.”

If the research reaches the stage of practical use, regulating gene manipulation will likely prove to be the next big hurdle.

The number of human genes has been estimated at more than 20,000. Some have been already identified, such as those that govern muscle power.

On a hypothetical level, it would be possible to create children with greater muscle power if those genes can be manipulated.

Experts have cited fears that parents might want tailor-made births, a return to eugenics, to ensure their offspring do not have disabilities.

The research panel asked the education and health ministries to establish a system to verify that each study is carried out appropriately.