Evolutions and stakes of genetic resources management.

For hundreds of years, intuitively or deliberately, farmers and breeders have taken advantage of the slow and constant renewal of genetic diversity in their domesticated plants or animals. Their management efficiently combines selection to maintain existing varieties or breeds and selection to extract new biological items meeting incoming necessities and environmental changes. The traditional practice is now criticized for three main reasons. The fear that it might not follow the accelerated occurrence of new demands and changes is one. The second derives from advances in biology and technology that indeed offer the expected answers provided the existence of residual diversity in present stocks. At last, the management of genetic resources is no longer the concern of specialists. Interest in the issue has been taken up by public opinions when they realized that genetic diversity is a component of overall biodiversity and that its intimate knowledge and uses transforms the vision of our relation to the living world. What is at stake today in genetic resources management is combining three selection approaches. The two traditional are still thoroughly relevant. A third one offers a process aiming at constant and random enrichment of the existing variety of diversity in domesticated plants and animals, and giving a major and renewed place to men' imagination and innovation.

Mitochondrial DNA: an advance in eukaryotic cell biology in the 1960s.

Between 1950 and 1960 mitochondria were recognized as well-characterized organelles of animal and fungal cells. They shared more functional autonomy than other cellular structures. The transmission of some mitochondrial characteristics did not obey Mendelian rules and followed cytoplasmic inheritance patterns. Was this situation a consequence of still unknown complexities? We present a personal account on how approaches were set up to test very different hypotheses. In the end, it was shown that mitochondria had their own DNA, mitochondrial DNA, and that this molecule carried information specific to these organelles.

Integrative biology and genetic resources management.

Integrative Biology is exemplified by a diversity of recently established collaborations to study the genetic diversity of the European rabbit, Oryctolagus cuniculus. Molecular markers were developed and used to investigate the link between wild population decreases or domestication procedures and possible losses of genetic diversity. Simultaneously, a European programme was launched for the management of genetic resources. The Integrative Biology approach shows that changes in genetic diversity are often buffered by the flexibility of rabbit reproductive systems. It appears, also, that all domestic animals belong to a subset of the wild genetic pool of their species without major loss of diversity despite exposure to severe viral infections. Consequently, management of genetic resources for production purposes and conservation or protection of declining Iberian wild populations require different approaches and measures.

ORGANIZATION AND REPLICATION ACTIVITY OF THE MITOCHONDRIAL MASS OF OOGONIA AND PREVITELLOGENIC OOCYTES IN XENOPUS LAEVIS.

The origin of the mitochondrial mass, previously well characterized in Xenupus diplotene oocytes, has been traced up to oogonia by means of electron microscopy. A polarized organization of the oogonia and of the oocytes of the succeeding stages was observed. The mitochondrial cloud was found to be built up in the centriolar region near the site where the chromosomes will be implanted along the nuclear envelope at the "bouquet" stage. Autoradiographic studies of thymidine incorporation into mitochondrial DNA suggest that mitochondrial DNA synthesis is active throughout this early period of oogenesis.