ZOO-FISH ANALYSIS IN INSECTIVORES - EVOLUTION EXTOLS THE VIRTUE OF THE STATUS-QUO

In evolutionary terms, insectivores are thought to be close to primate s. Through ZOO-FISH analysis using human chromosome-specific painting probes, the syntenic relationship between the human and common shrew, Sorer araneus, karyotypes was studied. The human karyotype was found t o be conserved in the shrew, with 32 autosomal segments of common synt eny. Special arrangements, already known from similar studies on other species, were noted: fusions of HSA 16 and 19, HSA 3 and 21, and HSA 14 and 15. Only 10 breaks are necessary to transform the human karyoty pe into the karyotype of the common shrew. Together with known ZOO-FIS H data from species belonging to other orders, this puts the human kar yotype arrangement near the basis of all mammalian karyotypes. Human c hromosome 2 was found to be conserved in its entirety as a single chro mosome arm in the shrew. Evidence is presented that the same fusion of two original chromosomal segments formed the shrew chromosome ortholo g of HSA 2 as the fusion that occurred during primate evolution to for m human chromosome 2. This is a remarkable example of chromosomal coev olution.