Document Type




Format of Original

15 p.

Publication Date



Oxford University Press

Source Publication

Nucleic Acids Research

Source ISSN


Original Item ID

doi: 10.1093/nar/13.1.73


We have investigated the timing of DNA synthesis, methylation and degradation during macronuclear development in the ciliate, Tetrahymena thermophila. DNA synthesis was first detected in the anlagen early in macronuclear development, but the majority of DNA synthesis occurred later, after pair separation. Anlagen DNA was first detectably methylated at GATC sites 3–5 hours after its synthesis. Once initiated, de novo methylation was rapid and complete, occurring between 13.5 and 15 hours of conjugation. The level of methylation of GATC sites was constant throughout the remainder of conjugation, and was similar to that in mock-conjugated cells. Degradation of DNA in the old macronucleus and DNA synthesis in the anlagen began at about the same time. Upon pair separation, less than 20% of old macronuclear DNA remained. A small percentage of nucleotides prelabeled prior to conjugation were recycled in the developing analgen.


Published version. Nucleic Acids Research, Vol. 13, No. 1 (January 1985): 73-87. DOI. © Oxford University Press 1985. Used with permission.

Kathleen Karrer was affiliated with Brandeis University at the time of publication.

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