Lima-de-Faria A, Arnason U, Widegren B, Isaksson M, Essen-Möller J, Jaworska H
Biosystems. 1986;19(3):185-212. doi: 10.1016/0303-2647(86)90039-0.
The Cervidae show the largest variation in chromosome number found within any mammalian family. The eight species of deer which are the subject of this study vary in chromosome number from 2n = 70 to 2n = 6. Three species of Bovidae are also included since they belong to a closely related family. Digestion of nuclear DNAs with the restriction endonucleases Hae III, Hpa II, Msp I, Eco RI, Xba I, Pst I and Bam HI reveals that there is a series of highly repetitive sequences forming similar band patterns in the different species. There are two bands (1100 and 550 base pairs) which are common to all species although the two families separated more than 40 million years ago. To obtain information on the degree of homology among these conserved sequences we isolated a Bam HI restriction fragment of approximately 770 base pairs from red deer DNA. This sequence was 32P labeled and hybridized by the Southern blot technique with DNAs cleaved with Bam HI, Eco RI, Hpa II and Msp I. Moreover, the same sequence was cloned in the plasmid vector pBR322 nick translated with 32P and hybridized with the DNAs of 8 species of Cervidae and 3 of Bovidae. The same cloned probe was labeled with 3H and hybridized in situ with the metaphase chromosomes of red deer (2n = 68) and Muntiacus muntjak (2n = 7 male). Homologies are still present between the highly repetitive sequences of the 8 species of Cervidae despite the drastic reorganization that led to extreme chromosome numbers. Moreover, the cloned DNA sequence was found to occupy the same position, in the proximal regions of the arms, in both red deer (2n = 68) and M. muntjak (2n = 7 male) chromosomes. The ribosomal RNA genes and the centromeres in these species have also maintained their main territory despite the drastic chromosome reorganization. These results are experimental confirmation of the chromosome field theory which predicted that each DNA sequence has an optimal territory within the centromere-telomere field and tends to occupy this same territory following chromosome reorganization.
鹿科动物在所有哺乳动物科中染色体数目变化最大。本研究的八种鹿的染色体数目从2n = 70到2n = 6不等。还包括三种牛科动物，因为它们属于亲缘关系密切的科。用限制性内切酶Hae III、Hpa II、Msp I、Eco RI、Xba I、Pst I和Bam HI消化核DNA，结果显示存在一系列高度重复序列，在不同物种中形成相似的条带模式。有两条带（1100和550个碱基对）在所有物种中都存在，尽管这两个科在四千多万年前就已分开。为了获得这些保守序列之间的同源程度信息，我们从马鹿DNA中分离出一个约770个碱基对的Bam HI限制性片段。该序列用32P标记，并通过Southern印迹技术与用Bam HI、Eco RI、Hpa II和Msp I切割的DNA杂交。此外，相同的序列克隆到质粒载体pBR322中，用32P进行缺口平移，并与八种鹿科动物和三种牛科动物的DNA杂交。相同的克隆探针用3H标记，并与马鹿（2n = 68）和小麂（2n = 7雄性）的中期染色体进行原位杂交。尽管发生了导致极端染色体数目的剧烈重组，但八种鹿科动物的高度重复序列之间仍然存在同源性。此外，发现克隆的DNA序列在马鹿（2n = 68）和小麂（2n = 7雄性）染色体的臂的近端区域占据相同的位置。尽管染色体发生了剧烈重组，但这些物种中的核糖体RNA基因和着丝粒也保留了它们的主要区域。这些结果是染色体场理论的实验证实，该理论预测每个DNA序列在着丝粒 - 端粒场内有一个最佳区域，并且在染色体重组后倾向于占据相同的区域。
