Studies on the DNA of Xenopus laevis oocytes

Open Access
Publisher Website
Google Scholar
Abstract
The existence of substantial amounts of deoxyribonucleic acid (DNA) in the cytoplasm of amphibian eggs is no longer a matter of discussion (review, Brachet, 1957). However, their intracellular distribution, role and origin remain controversial. According to Dawid (1965, 1966), the bulk of the egg cytoplasmic DNA in Xenopus is of mitochondrial origin. His method of phenol extraction isolates only high molecular weight DNA. On the other hand, Baltus & Brachet (1962) found that 65% of the DNA of Pleurodeles eggs sediments at low centrifugal speed and suggested that this nucleic acid is localized in the yolk platelets. This conclusion was based on chemical estimations of the total DNA present in the egg; they found values about 10 times higher than those presented by Dawid (1966). Brachet & Ficq (1965) confirmed that, in ovaries of Pleurodeles labelled with 14C-actinomycin, either in vivo or on histological sections, most of the radioactivity detected by autoradiography is concentrated in the yolk.