ABSTRACT
The dorsal or the ventral cortex of Xenopus laevis eggs, at the one- or two-cell stage, has been slightly injured with a microneedle; 184 of these eggs have been examined cytologically.
The frequency of early (cleavage) and late (gastrulation, neurulation) abnormalities after dorsal injury was about twice that after ventral injury.
Abnormalities of the mitotic apparatus and of the chromosomes are very frequent during cleavage after slight cortical damage.
At later stages, the previously wounded embryos often display aneuploidy, as shown by cytophotometric measurements of the DNA content of the individual nuclei. Aneuploidy is much more frequent after injury of the dorsal cortex than injury of the ventral cortex.
Autoradiography studies have shown that there is a close correlation between morphogenesis and nuclear RNA synthesis.
The results are discussed in relation to current ideas on the morphogenetic and genetic significance of the grey crescent and its cortex.
