Specific amino acid content and codon usage account for the existence of overlapping ORFS

Here we present a novel hypothesis for the origin of overlapping open readi ng frames (O-ORFs) observed in the 'non-coding frames' of several genes of yeast chromosome II. By computer analysis it was found that the specific am ino acid content and base distribution pattern at certain genomic locations and the presence of O-ORFs were related. This observation prompt us to con clude that these O-ORFs are mere statistical curiosities without any biolog ical function, which is in contrast to the hypotheses proposed by other aut hors. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.