Ancient genes of Saccharomyces cerevisiae.

Amber is a plant resin mainly produced by coniferous trees that, after entrapping a variety of living beings, was subjected to a process of fossilization until it turned into yellowish, translucent stones. It is also one of the best sources of ancient DNA on which to perform studies on evolution. Here a method for the sterilization of amber that allows reliable ancient DNA extraction with no actual DNA contamination is described. Working with insects taken from amber, it was possible to amplify the ATP9, PGU1 and rRNA18S ancient genes of Saccharomyces cerevisiae corresponding to samples from the Miocene and Oligocene. After comparison of the current genes with their ancient (up to 35-40 million years) counterparts it was concluded that essential genes such as rRNA18S are highly conserved and that even normal 'house-keeping' genes, such as PGU1, are strikingly conserved along the millions of years that S. cerevisiae has evolved.