Localization of cloned, repetitive DNA sequences in deer species and its implications for maintenance of gene territory.
The deer family shows the largest variation in chromosome number known in mammals (2n = 6 to 2n = 70). The drastic rearrangement of the chromosomes allows to test the prediction, based on the chromosome field theory, according to which DNA sequences tend to occupy specific territories within the eukaryotic chromosome. Nuclear DNAs were isolated from eight Deer and two Bovidae species. These DNAs were cleaved with the restriction enzymes Eco RI and Alu I. Following Eco RI digestion highly repetitive sequences formed two bands which were common to all deer species. These bands had about 1520 and 2240 base pairs and were particularly clear in Capreolus capreolus (2n = 70, roe deer). The 1520 band DNA was cloned in plasmid pUC9, nick translated, and hybridized with the DNAs of all ten species. The Capreolus DNA showed a high homology with the DNAs of all the species including the Indian muntjac (Muntiacus muntjak, 2n = 7, male) and the Chinese muntjac (Muntiacus reevesi, 2n = 46). 3H hybridization was carried out in situ with metaphase chromosomes of Cervus elaphus (2n = 68, red deer), M. muntjak, and M. reevesi. In C. elaphus all the chromosomes are heavily labeled except the regions of the arms near the centromere. In the muntjacs all chromosomes and most regions appear to be labeled. These results were checked with a different technique that involved the use of two antibodies and biotin labeling of the DNA. The hybridization picture was essentially the same as obtained with 3H. These results disclose that the 1520 bp DNA piece maintains its main territory independently of the drastic changes in chromosome number.