The Lampbrush Chromosomes of Amphibians

Abstract

The lampbrush chromosomes correspond to a special organization taken by the chromosomes in the female germ line during oogenesis in several vertebrates and invertebrates, when the oocyte is in the growth phase and its nucleus, the germinal vesicle, is arrested in the prophase of first meiotic division. Nevertheless, these chromosomes are not susceptible to analysis in all the groups and have been studied mostly in amphibians and birds. For the amphibians the lampbrush chromosomes have been mapped essentially in urodeles and a few anourans (Callan, 1986). In the present work we have selected an urodele, the Pleurodele, as a model. This animal reproduces well in captivity and consequently it is often used in embryological studies. The lampbrush chromosomes of Pleurodeles have been used for cytogenetic analysis, especially for the detection of chromosomal alterations. They have also been used for identification of natural populations and isolation of lineages having specific markers on the lampbrush chromosomes (Gallien et al., 1965; Jaylet, 1967 and 1972; Labrousse, 1966, 1970 and 1971; Lacroix, 1968a and b; Lacroix and Loones, 1971 and 1974). The basic method tor the preparation of lampbrush chromosomes is the same for all amphibian species, but specific adaptations may be necessary for each species (see Callan, 1986, and Gallet al, 1991).