Dry yeast, active dry and instant, is sold in packets, usually in a set of three. Each standard envelope contains about 2 1/4 teaspoons of yeast. By weight, that's 7 grams or 1/4 ounce.

In the proteomics push, brewer's yeast, Saccharomyces cerevisiae, is creating yet another mold. "[It has been] a huge leg up to have [the yeast genome] available for the last seven years," says John ...