Intraindividual chromosomal polymorphism in green sunfish (Lepomis cyanellus) as evidence of somatic segregation

Of 30 adult specimens of green sunfish, <i>Lepomis cyanellus</i>, obtained from a fish farm in southern California, 16 were heterozygous for a single Robertsonian translocation while 12 carried no translocation; the remaining two were homozygous for a translocation. In each heterozygote, the three cell types coexisted: the original heterozygous set (2n = 47, one metacentric) and the two homozygous sets (2n = 48, no metacentric, and 2n = 46, two metacentrics). No intraindividual chromosomal polymorphism was evident in those specimens which carried no translocation as well as in those which were homozygous for a translocation.

Sex-linkage of erythrocyte glucose-6-phosphate dehydrogenase in two species of wild hares

Glucose-6-phosphate dehydrogenase specific to the erythrocytes of each of two wild hares found in Europe was discerned by starch-gel electrophoresis at pH 7.0 and pH 8.6. The single, sharp band of the dehydrogenase of Lepus europaeus was faster than that of L. timidus, at both pH levels. The sex-linkage of this enzyme was tested through reciprocal hybrids between the two species. Each male hybrid had a single band of enzyme identical with that of its mother, while both parental types of this enzyme coexisted in female hybrids. Thus, sex-linkage of glucose-6-phosphate dehydrogenase has been suggested not only in man and in the family Equidae, but now in the family Leporidae of placental mammals as well.

Embryological basis for germ cell chimerism in mammals

That blood cell chimerism of dizygotic twins is accompanied by germ cell chimerism was suggested by previous demonstrations of the presence of female metaphase figures in the testis of males born twin to genetic females in cattle (Ohno <i>et al</i>., 1962) and the marmoset (Benirschke and Brownhill, 1963). The present findings in cattle on fetal triplets only 12 mm in crown-rump length furnishes the embryological basis for the observed phenomenon of germ cell chimerism. The liver of each triplet contained both male and female metaphase figures; cell chimerism was already established in all three. A histochemical test on alternate serial transverse sections revealed that alkaline-phosphatase-positive primordial germ cells were still in the middle of migration from the yolk sac to the developing gonadal ridges. A number of alkaline-phosphatase-positive cells were found within blood vessels, particularly within the venous sinusoids of the liver. They were interpreted to be primordial germ cells which had wandered into the blood stream.