Editing Sup35p (section)

==Adenine Pathway==

The phenotypic differences between [psi-] and [psi+] is made clear when the ability of the cell to make [[adenine]] is tampered with. The buildup of P-ribosylamino imidazole (AIR) (a precursor in the [[adenine pathway]] in yeast) induces a red pigment in a yeast colony visible to the naked eye. In isogenic strains where the non-sense mutation is in the middle of either the gene ADE 2 or ADE 1 (enzymes involved in the pathway), the [psi-] strain has either build ups of P-ribosylamino imidazole (AIR), or P-ribosylamino imidazolecarboxylate (CAIR), respectively. Because CAIR converts back into AIR if the enzyme that catalyzes it to the next precursor is absent, either mutation will cause a red color in the [psi-] strain. The [psi+] strain appears white even when subjected to the same non-sense mutations. Thus, it is inferred that the eRF3 of the [psi+] is non-functional.<ref>{{cite web | last = Montelone | first = Beth A. | name-list-style = vanc | title = Frequently Asked Questions--Yeast Strains. | publisher = Physics Department at Kansas State University. | date = 24 December 2009 | url = http://www.phys.ksu.edu/gene/GENEFAQ.html }}</ref>

This phenomenon is because the eRF3 in [psi-] is able to disconnect the ribosome effectively, so the enzyme cannot be properly synthesized. However, in the [psi+] strain, the enzyme is able to be synthesized enough so that the pathway still successfully produces adenine.