Replicative and chronological life-span assays.

Life-span assays in yeast are invaluable in characterizing the functions of gene products on cellular aging. Replicative life-span (RLS) is a measure of the number of divisions an individual cell can undergo. In this assay daughter cells are removed using a tetrad dissection microscope with a micromanipulator and scored. Chronological life-span (CLS) measures the length of time nondividing cells survive. A culture is grown to stationary phase with samples removed over time to assess the survival within the population. The strength of the yeast system lies in the ease of genetically manipulating genes of interest and the evolutionarily conserved nature of the genes found to influence longevity. Here, we describe methods used to measure yeast RLS and CLS.