Spore Analysis and Tetrad Dissection of .

Here we describe the processing of spores in batches (random spore analysis) or through tetrad dissections. Spores are usually prepared from matings between haploid strains (producing zygotic asci) or from sporulating diploids (producing azygotic asci). In random spore analysis, a snail enzyme preparation is used to digest the walls of asci to release free spores that are diluted and plated to form colonies. In tetrad dissection, a needle attached to a micromanipulator is used to pick asci and separate spores. Tetrad dissection has traditionally been the method of choice for genetic mapping and is very useful in the study of genetic interactions (e.g., suppressor analysis). It is also the preferred method for routine crosses because it ensures that every colony stems from a single spore. This can never be certain in random spore analysis.