Gene Maps of Marsupials.

Abstract

Increased interest in the structural characteristics of mammalian genomes, together with rapid advances in mapping technology, have led to the explosive expansion of gene mapping activity in recent years. Species for which gene mapping data were virtually nonexistent just a decade ago now possess substantial and serviceable gene maps that are enabling the localization of economically and biomedically relevant loci and are contributing to a fuller understanding of genome evolution and the relationships between genome structure and gene function. Recent progress in the compilation and effective application of gene mapping data has been particularly evident in the fascinating group of species that comprise the mammalian infraclass Metatheria, better known as marsupial mammals. As late as 1988, only 22 marsupial genes had been reported as mapped by any method in any species (a gene is considered mapped if it adheres to any of the following criteria: (1) assigned to a specific chromosome; (2) a member of a linkage group; (3) autosomal in marsupials but known to be X or Y linked in eutherians). These few gene assignments were achieved by a variety of methods, and were scattered piecemeal among a dozen different species (this number excludes 14 additional species in which 1 or more ribosomal RNA (RNR) genes were the only loci mapped [Hayman and Rofe 1977; Hayman and Sharp 1981; Young and others 1982]). As a consequence, few species had more than 2 or 3 genes mapped, and only 1 species could boast as many as 9 gene assignments. Currently, at least 142 loci have been assigned to physical locations or linkage groups in marsupials, and more than 15 species have at least 3 gene assignments. Most important, 2 distantly related species, Macropus eugenii (tammar wallaby) with 70 loci mapped and Monodelphis domestica (gray, short-tailed opossum) with 69