Date of Award:
Master of Science (MS)
Animal, Dairy, and Veterinary Sciences
Thomas D. Bunch
A cell synchronization technique was used that consistently yielded numerous elongated chromosomes, which are necessary for producing high-resolution G-banding. The prometaphase stage of contraction was determined to have the greatest utility for detailed comparative analysis and, therefore, was used in the preparation of the proposed standard high-re solution karyotypes and idiogram.
A proposed standard high-resolution G-band karyotype of the domestic sheep and goat is presented, along with a high-resolution G-band idiogram of the goat. The karyotypes presented contain considerably more bands than contemporary karyotypes and provide much greater resolution for linear differentiation. The X chromosome of the sheep is acrocentric, rather than having a minute p arm as recently reported.
A side -by-side comparison of high-resolution G-band sheep and goat chromosomes indicates identical equivalence of banding patterns. Of special note is the homology of banding patterns for the six acrocentric autosomes of the goat and the respective three submetacentric autosomes of the sheep, reinforcing the evidence that the goat is representative of the ancestral karyotype.
C-bands and NORs of the sheep and goat are also presented. When C-banded, the centromeric regions of the sheep and goat acrocentric autosomes were found to be densely stained. The centromeric regions of the X and Y, however, were not stained differently from the chromosome arms. In the sheep submetacentrics, chromosomes 1 and 3 showed weak C-bands while chromosome 2 showed stronger bands.
In the sheep and goat, 10 NORs located terminally on five chromosomes pairs were found. Sheep NORs occurred on the three pairs of submetacentric autosomes and on one large and one small pair of acrocentric autosomes. Goat NORs occurred on four large and one small pair of acrocentric autosomes. Sine the banding patterns obtained when staining for NORs do not permit individual identification of each chromosome, duplicate G-banding and silver staining of elongated chromosomes of both sheep and goat would need to be conducted to identify specific NOR-bearing chromosomes.
Mensher, Stephen H., "Comparative Study of Elongated Chromosomes in Sheep and Goats and a Proposed Standard" (1987). All Graduate Theses and Dissertations. 4065.