The promises were never modest. There would be powerful new medicines and hardy new plants and animals. But one of the first products coming from genetic engineering turns out to be -- ready for this? -- liquid drain opener.

Such mundane products as this may be the near-term hope of the genetics business, which has been battered by sick financial statements and a loss of investor confidence. Genex Corp. has pointed much of its effort at products with broad market appeal and a relatively short development time. To make a bathroom drain opener, it extracts a hair-dissolving enzyme from bacteria and wholesales a solution of the stuff for $4 a quart. Assuming no regulatory problems, Genex will eventually use genetic engineering to rev up production.

At four uses a quart, Genex's Proto costs slightly more than liquid Drano. But Genex hopes that such customers as hotels, hospitals, and office buildings will pay extra for a noncaustic product. Proto may open not only drains, but also the pipeline of new products long hyped by genetics companies.