Figure 2.

The ‘Strathern model’ for [PSI] inheritance. Fortuitous or induced read-through of the UAA codon generates a protein (hypothetical) that sustains itself by promoting reading through its own internal stop codon and also, incidentally, any other codon mutations to UAA in other genes. The suppression ('[PSI⁺]') phenotype so generated would be dominant and inherited in non-Mendelian fashion since it does not depend on any change in DNA sequence, only in its activity.