How do you make yeast work harder? Not to make bread, but in processes that yield chemicals and pharmaceuticals. Industries currently use a yeast called Saccharomyces cerevisiae. They’d like it to work better. The answer is in manipulating the yeast’s genetic code. To get at that code, researchers developed a method that turns off targeted genes in the yeast, introducing mutations. The team’s approach deletes specific points in the DNA sequence. They study how each deletion affects the yeast. Does a deletion cause the yeast to stop working in certain chemicals? Does a deletion make the yeast grow more slowly? The team’s approach lets them study each gene, as well as in combination with other genes. With this approach, scientists can construct libraries of mutants for use in discovering how each gene works.