Saccharomyces cerevisiae's ability to form the prion [PSI ] may increase the rate of evolvability, defined as the rate of appearance of heritable and potentially adaptive phenotypic variants. The increase in evolvability occurs when the appearance of the prion causes read-through translation and reveals hidden variation in untranslated regions. Eventually the portion of the phenotypic variation that is adaptive loses its dependence on the revealing mechanism. The mechanism is reversible, so the restoration of normal translation termination conceals the revealed deleterious variation, leaving the yeast without a permanent handicap. Given that the ability to form [PSI ] is known to be fixed and conserved in yeast, we construct a mathematical model to calculate whether this ability is more likely to have become fixed due to chance alone or due to its evolvability characteristics. We find that evolvability is a more likely explanation, as long as environmental change makes partial read-through of stop codons adaptive at a frequency of at least once every million years.
You have requested a machine translation of selected content from our databases. This functionality is provided solely for your convenience and is in no way intended to replace human translation. Neither BioOne nor the owners and publishers of the content make, and they explicitly disclaim, any express or implied representations or warranties of any kind, including, without limitation, representations and warranties as to the functionality of the translation feature or the accuracy or completeness of the translations.
Translations are not retained in our system. Your use of this feature and the translations is subject to all use restrictions contained in the Terms and Conditions of Use of the BioOne website.
Vol. 57 • No. 7