Courtesy of University of California, San Francisco

The science of yeast genetics was still in its infancy some 30 years ago, and one of its thorniest problems wouldn't go away: How do diploid yeast cells transform themselves into haploid cells, so that they can mate and reproduce through meiosis? A young University of Oregon researcher named Ira Herskowitz proposed that a cassette of DNA dropped out, only to be replaced by a copy of another cassette of DNA, and that this event altered the very cell type. "It was such a simple yet beautiful solution," says yeast geneticist Brenda Andrews, University of Toronto. "And his drawings [known in the field as 'Iragrams'] were always just as beautiful." The cassette model of mating-type interaction (the image above was shown during Herskowitz' first presentation on the subject), has since become a pillar of modern yeast genetics.

--Sam Jaffe

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