Sex chromosome chimaerism and the transmission of blood group genes by tetraparental rams.

A previously published study of 4 rams, 3 of them tetraparental chimaeras, has been extended. All were born subsequent to transplantation of separated blastomeres into intact 4--8-cell embryos which were transferred to recipient ewes. All were phenotypically normal males. Study of blood lymphocytes and red cell antigens showed that two were XX/XY chimaeras, one an XY/XY chimaera. Chimaerism was not identified in the 4th animal. The new data show that the previously reported decline in proportions of red cells derived from the one cell line has continued, although the proportions of lymphocytes entering mitosis in culture have remained nearly constant. A decline of potassium concentration in the red cells of one animal and of transferrin type in another also continued. Analysis of blood types in the offspring of the 4 rams revealed that both cell lines of the XY/XY chimaera must have produced functional spermatozoa whereas the genes transmitted by the remaining 3 rams gave evidence of spermatozoa from one cell line only.