Inferring genes from open reading frames

One expects that in DNA without protein coding function, stop codons (which constitute three of the 64 possible codons) should occur frequently in all reading frames, and that a long open reading frame (ORF) can be interpreted as a sign for the existence of a gene. We make a beginning on introducing quantitative measures of confidence into this inference--taking Saccharomyces cerevisiae as a sample case--and show that some common assumptions can reasonably be questioned. In particular we show that statistical support for the biological function of shorter ORFs listed as putative genes in recent papers is in fact very weak. This is an issue of practical as well as theoretical interest, since researching the function of a putative gene is difficult and expensive.