n. (in genetics) a structure consisting of homologous chromosomes attached to each other by *chiasmata during the first division of *meiosis. —bivalent adj.
n. (in genetics) 1. the four cells resulting from meiosis after the second telophase. 2. the four chromatids of a pair of homologous chromosomes (see bivalent) in the first stage of meiosis.... tetrad
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