First report of GTG-banded nomenclature of Pakistani Lohi sheep (Ovis aries)
The present study was planned to generate the G-band nomenclature of the commonly occurring Lohi sheep breed in the Punjab province of Pakistan. Whole blood samples were collected through jugular venepuncture in heparinised vacutainers. The metaphase slides were prepared using standard protocols. The results from microscopic screening of 50 good quality metaphase cells from each animal were studied and they revealed a chromosome complement of 54, XX and XY in Lohi sheep. The first 3 pairs were sub/metacentric whereas the other autosomes, including X, were classed as acro/subacrocentric. The Y chromosome was the smallest metacentric chromosome and had a star-like presentation. The trypsinisation time for optimal G-bands was highly variable, and individual chromosomes were identified by G-positive and negative band markers. The identification of chromosomes 4 & 6, 8 & 9, and 19-26 was difficult because these chromosomes were indistinct and small. The X chromosome was the largest sub/acrocentric, with a prominent G-positive band along the lower middle length. Complete G-band homology was noticed between Lohi and other reported sheep breeds from different parts of the world. The G-band ideogram of Lohi was also constructed based upon the G-band organisation observed in the Lohi genome. None of the 350 metaphase cells studied revealed chromosomal abnormalities.
Key words: Lohi sheep, karyotype, GTG bands, Pakistan, cytogenetics