In early April 1983, a stranded Malaysian gaur (Bos gaurus hubbacki) mated
with a group of Sahiwal-Friesian dairy heifers and this resulted in the birth of
an inter-specific hybrid calf named SELEMBU. In this study, chromosome
analysis of four Malayan gaur (Bos gaurus hubbacki), ten Sahiwal-Friesian
cattle and seven hybrid backcrosses was undertaken to determine their
karyotype status and differences.
The gaur and cattle has chromosome complements of 2n = 56 and 2n = 60,
respectively. Two types of chromosomal arrangements of the backcrosses
were observed; namely an intermediate to the parental species (2n = 58) and
a cattle type (2n = 60). The backcrosses with 2n = 60 shared similar
chromosomal arrangement and banding characteristics of the cattle. Backcrosses with 2n = 58 exhibited the non-homology of two submetacentric and two acrocentric autosomes, where the variations were inherited from the
parental species that possessed different karyotypes.
A comparison of the gaur with cattle, as the model of the ancestors of the
modern bovids, showed structural and characteristic differences in their
karyotypes. The gaur exhibited two pairs of submetacentric chromosomes
and lacked two chromosome pairs, which had resulted from Robertsonian
translocations during their karyotype evolution. Banded karyotypes revealed
extensive similarities of chromosomes 1 and 2 of the Malayan gaur to the
homologous acrocentric chromosomes of cattle. For the first time,
chromosome 1 of the gaur was identified to contain an ancient origin inverted
segment compared to cattle, which was homozygous in all the studied gaur
samples. The intensity of the C-bands on chromosomes 1 and 2 suggested
that the translocations occurred at different periods of time during the
karyotype evolution
