Leukocyte and skin cultures of a female hybrid between a donkey and Grevy zebra show a diploid chromosome complement of 48. From this finding it is inferred that the Grevy zebra is characterized by 2n=34 and that such hybrid's regular infertility is analogous to that of mules and hinnies.
Barr bodies were present in the tissue-cultured cells and studies with tritiated thymidine show that Barr body and the chromosome set replicate asynchronously. One large element corresponds to the late replicating X of other species and often possesses the morphologic features of a donkey X. At other times it is decidedly more metacentric, a quality tentatively assigned to the Grevy zebra X. Not enough cells could be studied to determine whether random or selective late replication (? inactivation) of one or the other of the sex chromosomes takes place. It is suggested that the study of such hybrids may yield cytologic information concerning the lyon hypothesis.
KeywordsMorphologic Feature Developmental Biology Thymidine Infertility Large Element
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