SCIENTISTS have a long way to go to synthesize a living molecule, let alone understand how organic life arose on this planet. But if "test-tube life" remains a distant goal, those pursuing it have also come a long way in their quest. The test-tube synthesis of a "living" virus illustrates this point.Whether viruses really are "alive" in a basic biological sense is debatable. They are molecular entities that invade living cells and use the cells' chemical machinery to reproduce themselves. Biologists consider self-replication a basic characteristic of organic life. But they are undecided as to whether the virus's parasitic use of cellular machinery qualifies as true self-reproduction. Nevertheless, viruses are close to the line between living and nonliving matter, whichever side of that line they occupy. Thus the laboratory synthesis of a fully functional virus gives molecular biologists an important new tool with which to study the basic nature of organic life. Biologists had thought it impossible for a virus to replicate outside a living cell. The main significance of the achievement of Akhteruzzaman Molla, Aniko V. Paul, and Eckard Wimmer of the State University of New York at Stony Brook is the simple fact that they were able to do it at all. In their report of this work in the current (Dec. 13) issue of the journal Science, they tell of synthesizing a polio virus that made millions of copies of itself. While this replication took place outside a living cell, it did have the help of essential cellular machinery. The microbiologists' brew contained human ribosomes - a cell's protein-making machinery - as well as the raw materials and genetic instructions for making the virus. Now the researchers plan to try synthesizing other virus types. They also will systematically eliminate substances from their brew to try to identify the essential materials for viral assembly. This should give medical researchers a new method for studying disease-related viruses. It also should help shed light on the early development of organic life. Two closely related types of molecules carry and implement the genetic instructions for making organisms from the simplest microbes to humans. Biochemists call them DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). A virus generally is a DNA or RNA molecule wrapped up in a protein coat. The molecule sheds this coat when it enters a cell. DNA usually carries the genetic blueprint. RNA generally plays a complementary role by transcribing those instructions and inducing cells to make substances needed for organisms to function and grow. But many microbiologists suspect that RNA may have been the original genetic carrier. The ability to synthesize RNA-based viruses gives these biologists a powerful new tool to study the genetic capabilities of this intriguing type of molecule. This should complement work in other laboratories in which microbiologists are studying the ability of RNA molecules - as distinct from intact viruses - to duplicate themselves. No one knows when, if ever, scientists will be able unambiguously to synthesize organic life. In fact, no one knows whether or not we will ever fully discover how such life arose on Earth. But scientists have made more progress in this difficult research than one might have expected even a decade ago.