Biological Organization at the Cellular and Supercellular Level: A Symposium Held at Varenna, 24-27 September, 1962, under the Auspices of UNESCO

By R. J. C. Harris | Go to book overview

THE ROLE OF THE NUCLEIC ACIDS
IN THE PROCESSES OF INDUCTION,
REGULATION AND DIFFERENTIATION
IN THE AMPHIBIAN EMBRYO AND THE
UNICELLULAR ALGA, ACETABULARIA
MEDITERRANEA

J. BRACHET

Université libre de Bruxelles, Bruxelles, Belgium


SUMMARY

The role of nucleic acids (DNA and RNA) during cleavage and differentiation in amphibian eggs is discussed, with special emphasis on the mechanisms of DNA synthesis in normal embryos and lethal hybrids, and on the RNA distribution during development.

The importance of the cell nucleus for RNA and protein synthesis in the unicellular alga Acetabularia mediterranea is discussed on the basis of recent experiments: it is suggested that ribosomal RNA lies under a much closer nuclear control than transfer and chloroplastic RNA's.

A hypothesis concerning the role of messenger and ribosomal RNA in morphogenesis is presented.


INTRODUCTION

In the following, a summary is presented of current knowledge about DNA, RNA and protein interactions during morphogenesis. Two biological systems, amphibian eggs and the unicellular alga Acetabularia, both of which have been extensively studied in our laboratory, win be discussed from that viewpoint. The present report will end with an attempt to integrate the biological and biochemical observations made on these two morphogenetic systems in a more general hypothesis of differentiation, at the molecular level.


EXPERIMENTAL EVIDENCE

A. Amphibian eggs development

1. DNA synthesis during development

Multiplication of the cell nuclei, during cleavage, is an obvious requirement for the morphogenetic movements characteristic of gastrulation and neurulation: only relatively small cells have the plasticity required for this phase of development.

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