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(plural tetrads) 1  A group of four things. ( 2 chemistry) A tetravalent atom or radical. ( biology) Two pairs of sister chromatids (a dyad pair) aligned in a certain way and often on the equatorial plane during the meiosis process.
Abstract. One hundred and forty-eight temperature-sensitive cell division cycle (cdc) mutants of Saccharomyces cerevisiae have been isolated and characterized. Complementation studies ordered these recessive mutations into 32 groups and tetrad analysis revealed that each of these groups defines a single nuclear gene.