PARALLELISM IN CHIMERIC RATIOS IN HETEROSEXUAL CATTLE TWINS

INCE the discovery of chimerism in bone marrow and gonads of heterosexual cattle twins (OHNO, TRUJILLO, STENIUS, CHRISTIAN and TEPLITZ 1962) several reports have appeared in the literature on blood cell chimerism in twins and multiple births in cattle (KANAGAWA, KAWATA and ISHIKAWA 1965; BASRUR and STOLTZ 1966; KANAGAWA and BASRUR 1968). Examination of cultured leukocytes of these chimeric cattle revealed that both members of the twin pairs or all members of any particular set of multiple births, carry similar proportions of male and female cells in the peripheral blood. Since a tendency for preponderance of one cell type was generally apparent in all members belonging to any set of chimeras ( KANAGAWA, KAWATA, ISHIKAWA, MURAMOTO and ONO 1965; BASRUR and STOLTZ 1966), a detailed study of chimeric pattern in twins and co-borns of multiple births was undertaken with a view to comparing the trend in our own studies with that reported by some of the other investigators in this field.