The karyotype of the domestic sheep (Ovis aries) identified by quinacrine mustard staining and fluorescence microscopy.

Abstract

The modal chromosome number of the domestic sheep (Ovis aries) is 54. It is possible to identify 25 out of the 27 pairs of chromosomes by means of quinacrine mustard staining and fluorescence microscopy. There is often a considerable difference in length between the homologues of the same pair. The submetacentric autosomes may be derived from the basic karyotype of the family Bovidae by Robertsonian fusion. Consequently, the karyotype of the sheep chromosomes has been arranged in another way than in the goat and cattle. The Q-band pattern of the sheep autosomes is identical with that of the goat autosomes, except the Robertsonian fusions, and with cattle autosomes, except Pair No. 16. In the sheep, the X chromosome is one of the largest chromosomes of the karyotype. Its relative length is about 0.5 per cent smaller than in the other two species studied. Nevertheless, the number of Q-bands in the X chromosome of the sheep seems to be the same as in the goat and cattle, but the sequence of the bands is different. The Y chromosome of the sheep is the smallest chromosome, and its fluorescence is identical with the Y chromosome of goat and cattle.