Oncor Inc. said Thursday that it has introduced the first DNAprobe to detect and screen for fragile X mutation, cause of themost common inherited form of mental retardation.

Oncor (NASDAQ:ONCR) of Gaithersburg, Md., is still negotiatinga final licensing agreement for rights to the probe.

Fragile X syndrome, which affects one in 1,500 males and onein 2,500 females, causes X chromosomes to break easily. Onein every 866 individuals is a carrier of the fragile X mutation.

Thirteen labs currently test for fragile X syndrome, usingrestriction fragment length polymorphism assays, but suchassays are considered difficult to evaluate. About 15,000 suchtests were performed in the United States in 1990. Oncor saidit expects the market to expand dramatically now that a bettertest is available, said Betty Wolf, product manager formolecular cytogenetics at Oncor.

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