Satellite associations of D- and G-group chromosomes are investigated in blood samples derived from the Down syndrome patients. The association shows a significantly increased tendency in cells from the Down syndrome patient than the normal population. The involvement of chromosome no. 21 in association is significantly excess.
In order to compare the sensitivity to radiations in the black and Norway rats, 400 to 750R γ-rays (Cs137) are exposured to males, and they are mated to the non-irradiated females. Rate of chromosome mutations in the offspring thus obtained is 0.02 in both species. A hypothesis by the present author, that the black rat with a higher occurrence of chromosome mutation in the natural population is due to the heavy exposure from the natural radiation, seems to be indirectly proved by the present work.
The banding patterns of the chromosomes of Hynobius tokyoensis Tago are obtained by the treatment of Sumner's BSG method with some modifications. These patterns enable the identification of 17 out of 28 pairs of chromosomes in this species. Morphologically similar chromosome pairs such as nos. 4 and 5, nos. 6 and 7, and nos. 10, 11 and 12 could be easily distinguished from one another.
The separation of human X- and Y-bearing sperm was achieved using free-flow electrophoresis. The mobility of X-bearing sperm was faster than that of Y-bearing sperm and the electrophoretic pattern showed the separated two main peaks. One nearer the anode contained only X-bearing sperm, whereas the other was mainly composed of Y-bearing sperm. This result indicates that the zeta potential on the cell surface of X-bearing sperm was higher than that of Y-bearing sperm.