(1947–    ), American biochemist and Nobel laureate, born in Chicago and educated at Grinnell College and the University of California at Berkeley. He joined the department of chemistry at the University of Colorado, Boulder, in 1978, becoming a full professor in 1983.

As assistant professor at the University of Colorado in 1978, Cech conducted research on ribosomal ribonucleic acid (RNA) in genes of a protozoan, Tetrahymena thermophila. He and his colleagues discovered that the deoxyribonucleic acid (DNA) they were working with had apparently been affected by an ENZYME, (q.v.) that had removed the introns (noncoding sequences) of the DNA. Working with a precursor RNA, they believed that they would have to purify their material to remove the enzyme they suspected was contained in cell nuclei under examination; however, the introns of the RNA had already been excised. Further research revealed that the RNA itself was a biological catalyst, the enzyme they were seeking, which they named a ribozyme; the findings were published in 1982.

Cech and the American molecular biologist Sidney Altman, who had independently obtained similar evidence, shared the 1989 Nobel Prize in chemistry for demonstrating that RNA was “both genetic code and enzyme at one and the same time.”