Micronucleus(redirected from Micronuclei, chromosome-defective)
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in infusorians, the smaller (generative) nucleus. The micronucleus is usually diploid and divides by mitosis; however, during the sexual process in infusorians (conjugation), it divides meiotically and gives rise to sexual nuclei or pronuclei. During the vegetative period, the genetic apparatus of the micronucleus remains inactive, does not synthesize ribonucleic acid, and has no influence on the phenotype of the organism.