Abstract
Asynchronous DNA replication of euchromatic (E) and heterochromatic (H) chromosomes and heterochromatic B chromosomes (B) were studied in the mealybug, Pseudococcus obscurus Essig (Homoptera: Coccoidea). The study was carried out on mycetocytes of adult females and on spermatocytes of mid-second instar males by employing tritiated thymidine labeling and autoradiography. In the mycetocytes the incorporation of the labeled thymidine began and ended later in the B's than in the E chromosomes. The S period was found to be about 21 hours. The DNA replication of the E chromosomes occupied about 86% of the S period and that of the B's 33%; during 18% of the mid-S period the replication of the two types of chromosomes overlapped. In the meiotic S period of the spermatocytes, the DNA of the E chromosomes started to replicate earlier than that of the H chromosomes and the B's, but the replication of the E chromosomes, the H chromosomes, and the B's overlapped. The H chromosomes completed their replication much later than the E chromosomes and slightly later than the B's.
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Supported by grants GB 1585 and GB 6745 to Dr. Uzi Nur from the National Science Foundation, Washington, D. C.
Part of a thesis submitted to the University of Rochester in partial fulfillment of the requirements for the degree of Doctor of Philosophy.
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Huang, CC. Replication of euchromatin and heterochromatin in a mealybug. Chromosoma 34, 230–242 (1971). https://doi.org/10.1007/BF00285188
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DOI: https://doi.org/10.1007/BF00285188