B-CHROMOSOME SYSTEMS IN THE GREATER GLIDER, PETAUROIDES-VOLANS (MARSUPIALIA, PSEUDOCHEIRIDAE) .2. INVESTIGATION OF B-CHROMOSOME DNA-SEQUENCES ISOLATED BY MICROMANIPULATION AND PCR

B chromosomes, despite their common occurrence throughout the animal a nd plant kingdoms, have not been investigated extensively at the molec ular level. While the majority of B chromosomes occurring in animals h ave been described as heterochromatic, only a few researchers have exa mined the DNA of these chromosomes beyond this gross cytological level . This is the case in the largest of the gliding marsupial possums, th e greater glider, Petauroides volans. To examine the molecular composi tion and localization of B-chromosome DNA sequences in P. volans, a co mbination of micro-manipulation and the polymerase chain reaction was used in this study to isolate and then amplify the DNA of the B chromo somes. Localization of the isolated B-chromosome sequences to metaphas e chromosomes was investigated using fluorescence in situ hybridizatio n. The B chromosomes in this species are shown to be composed of a het erogeneous mixture of sequences, some of which are unique to the B chr omosomes, while others exhibit homology to the centromeric regions of the autosomal complement.