Sublocalizing the centromeric region in linkage groups from three metacentric rat chromosomes by FISH

Traditionally, the mouse has been the rodent of choice for genetic experimentation, and this research has generated a large amount of mapping data in the mouse. As the focus of interest moves from monogenic diseases towards more complex disorders, the rat is becoming more popular as a genetic model since much physiological research on complex diseases has been performed in the rat. As a consequence, many suitable rat models are available for complex traits including hypertension, arthritis, diabetes, cancer, seizures, and psycho-behavioral disorders. In order to improve the usefulness of the rat as a genetic model, the genetic and physical maps of the rat need to be expanded. Furthermore, a more efficient use of the available mapping data would be possible if the relationship between the two types of maps could be improved and clarified. For instance, if enough anchor points existed, interjacent markers on the linkage maps could be translated into chromosomal locations without actually mapping them. Among the 21 chromosome pairs in the rat, the centromere is located interstitially in 5 submetacentric pairs and in 7 metacentric pairs. Presently, the approximate position of the centromere has been established only for Chromosomes (Chrs) 1 and 17. It is important to determine the centromeric position in metacentric/submetacentric chromosomes, because recombination frequencies often drop considerably near the centromeres, complicating comparisons between the physical and genetic maps. As a step to facilitate such comparisons, we have sublocalized the centromere positions on the linkage map for some of the metacentric rat chromosomes.