AbstractsBiology & Animal Science

Statistical data from breeding experiments suggested that a reciprocal chromosomal translocation had spontaneously occurred in a line of S. C. White Leghorn fowl. Approximately 50% of the embryos from matings between suspected translocation heterozygotes and normal birds died early during incubation. In an effort to obtain cytological proof of this translocation, mitotic and meiotic chromosomes from normal birds and translocation heterozygotes were studied. For study of mitotic chromosomes leucocytes obtained from peripheral blood were cultured in vitro. Mitosis was arrested with colchicine and the cells subjected to a hypotonic environment prior to fixation in Carnoy's acetic-alcohol. Air dried preparations of these cells were stained with Giemsa or Acetic-Orcein. For study of meiotic chromosomes testicular tissue was subjected to hypotonic treatment prior to fixation in Carnoy's. Cells were then resuspended in 45% acetic acid. Air dried preparations were stained with acetic orcein and viewed with phase contrast optics. Study of mitotic chromosomes revealed no demonstrable difference between normal birds and translocation heterozygotes. Examination of meiotic chromosomes from translocation heterozygotes showed an abnormal association of chromosomes two and three during diplonema and diakinesis. It appeared that the short arm of chromosome two and the long arm of chromosome three had undergone a mutual exchange of a small amount of chromatin material. The cytological demonstration of this unique spontaneous reciprocal translocation will aid in establishing relationships between gene linkage groups and their residual chromosomes.