Abstract
Chromatin diminution--the fragmentation and elimination of chromosome Regions--provides an unusual opportunity to study genomic reorganization during development. Some species of copepods regularly excise and discard large amounts of nuclear DNA from presumptive somatic cell lines during early cleavage stages . To study this phenomenon in M. edax we determined DNA-Feulgen levels for more than 5,600 individual nuclei from squash preparations of 30 female and 25 male adults collected from lakes in Nova Scotia, Virginia and Florida. Fixation in 3:1 methanol/acetic acid was followed by squashing individual specimens in 45% acetic acid, freezing each slide in liquid N2 and thawing in absolute ethanol before air drying. Each series of slides was stained with the feulgen reaction for DNA and measured with a Vickers M86 scanning and integrating microdensitometer at 560 nm, using chicken RBC nuclei as an internal reference standard of 2.5 pg DNA per cell. This allowed us to ask several questions: are there differences in genome size (1) among specimens from different collecting localities, (2) between females and males at any single locality, and (3) between cells of germ line and somatic cell lineages?
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Schedule a callMore From: Proceedings, annual meeting, Electron Microscopy Society of America
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