title: Karyotype analysis of mithun (Bos  frontalis) and mithun bull x Brahman cow hybrids.
abstract: We  examined the cytogenetics of mithun (Bos frontalis), a domesticated  version of the Asian gaur, and hybrids (F(1) generation)  produced by artificial insemination of Brahman cows (Bos indicus) with  mithun semen. Reproductive potential was also examined in the F(1) generation  and a backcrossed heifer for utilization of heterosis. Metaphase chromosome  spreads were examined by conventional staining and fluorescence in situ hybridization  hybridized with the entire chromosome 1 of mithun as a specific probe.  Chromosome 1 of mithun was found to be equivalent to Bos taurus chromosomes  2 and 28. The karyotype of the female mithun (N = 4) comprised 58 chromosomes,  including 54 acrocentric and four large submetacentric chromosomes, without the  four acrocentric chromosomes found in the domesticated species B. indicus.  However, one of the four female mithuns with a normal mithun phenotype had an  abnormal karyotype (2n = 59), indicating introgression from B. taurus or B. indicus. The F(1) karyotypes  (N = 6, 3♂3♀) of the mithun bull × Brahman cow cross had 2n = 59, intermediate  between their parents; they were consistent heterozygous carriers with a  centric fusion involving rob(2;28), as expected. Two pronounced red signals  were seen in the mithun karyotypes, three red signals in the mithun × Brahman  hybrids, and four red signals in the Brahman cattle, in good agreement with  centric fusion of bovine rob(2;28). The female backcross hybrid (N = 1) with 2n  = 59 had a similar chromosome configuration to the F(1) karyotypes  and had rob(2;28). Such female backcross hybrids normally reproduce; however,  the F(1) bulls (N = 3) had not yet generated normal sperm at 24  months.
authors.affiliation: College of Animal Science and Technology, Northwest A & F University, Yangling, Shaanxi, China.
authors.forename: K-X
authors.initials: KX
authors.lastname: Qu
authors.forename: Z-X
authors.initials: ZX
authors.lastname: He
authors.forename: W-H
authors.initials: WH
authors.lastname: Nie
authors.forename: J-C
authors.initials: JC
authors.lastname: Zhang
authors.forename: X-D
authors.initials: XD
authors.lastname: Jin
authors.forename: G-R
authors.initials: GR
authors.lastname: Yang
authors.forename: X-P
authors.initials: XP
authors.lastname: Yuan
authors.forename: B-Z
authors.initials: BZ
authors.lastname: Huang
authors.forename: Y-P
authors.initials: YP
authors.lastname: Zhang
authors.forename: L-S
authors.initials: LS
authors.lastname: Zan
mesh_terms: D059786:Abnormal Karyotype; D000818:Animals; D002417:Cattle / Q000235:genetics*; D002678:Chimera / Q000235:genetics*; D002875:Chromosomes; D003582:Cytogenetics; D004247:DNA; D005260:Female; D007315:Insemination, Artificial; D059785:Karyotype; D007621:Karyotyping / Q000379:methods*; D008297:Male
chemical_list: D004247:DNA