Abstract
Previous studies have indicated that certain sequences in the micronuclear genome are absent from the somatic macronucleus of Tetrahymena (Yao and Gorovsky, 1974; Yao and Gall, 1979; Yao, submitted). The present study used in situ hybridization to follow the elimination process during the formation of the new macronucleus. Micronuclear-specific DNA cloned in recombinant plasmids was labelled with 3H and hybridized to cytological preparations of T. thermophila at various stages of conjugation. Despite a smaller size and lower DNA content, the micronucleus has more hybridization than the mature macronucleus. Hybridization initially increased in the anlage (newly developing macronucleus) to reach a maximal level right after the old macronuclei had disappeared. The hybridization in the anlage then decreased to a significant extent prior to the first cell division. The results suggest that the micronuclear-specific sequence is first replicated a few rounds before it is eliminated from the anlage, and the elimination process occurs without nuclear division.
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Yokoyama, R.W., Yao, MC. Elimination of DNA sequences during macronuclear differentiation in Tetrahymena thermophila, as detected by in situ hybridization. Chromosoma 85, 11–22 (1982). https://doi.org/10.1007/BF00344591
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DOI: https://doi.org/10.1007/BF00344591