A molecular cytogenetic analysis of the tribe Bovini (Artiodactyla : Bovidae : Bovinae) with an emphasis on sex chromosome morphology and NOR distribution

Q-band comparisons were made among representative species of the four gener a of the tribe Bovini (Bos, Bison, Bubalus, Syncerus) as well as to selecte d outgroup taxa representing the remaining two tribes of the subfamily Bovi nae (nilgai, Boselaphini; eland, Tragelphini), the Bovidae subfamily Caprin ae (domestic sheep) and the family Cervidae (sika deer and white-tailed dee r). Extensive autosomal arm homologies were noted, but relatively few deriv ative character states were shared. Focus was then made on variation of the sex chromosomes and the chromosomal distribution of nucleolar organizer re gions (NORs). Bovine BAC clones were used in molecular cytogenetic analyses to decipher rearrangements of the sex chromosomes, and a pocket gopher 28s ribosomal probe was used to map the chromosomal locations of nucleolar org anizing regions (NORs). Some of the more noteworthy conclusions drawn from the comparative analysis were that: 1. The Bovidae ancestral X chromosome was probably acrocentric and similar to acrocentric X chromosomes of the Bovinae; 2. The domestic sheep acrocentric X is probably a deriative character state that unites non-Bovinae subfamilies; 3. Bos and Bison are united within the tribe Bovini by the presence of shar ed derivative submetacentric X chromosomes; 4. Sika and white- tailed deer X chromosomes differ by inversion from X chr omosomes of the Bovinae; 5. The Bovini ancestral Y chromosome was probably a small acrocentric; 6. Bos taurus, B. gaurus and B. banteng share derivative metacentric Y chro mosomes; 7. Syncerus and Bubalus are united by the acquisition of X-specific repetit ive DNA sequence on their Y chromosomes; 8. Bovinae and Cervidae X chromosome centromere position varies without con comitant change in locus order. Preliminary data indicate that a knowledge of the chromosomal distribution of NORs among the Bovidae will prove to be phylogenetically informative.