Chromosomal repatterning in crocodiles: C, G and N-banding and the in situ hybridization of 18S and 26S rRNA cistrons
- 1) Division of Natural Sciences, Museum of Arts and Sciences of the Northern Territory, P.O. Box 4646, Darwin, N.T., Australia
- 2) Department of Organismic and Evolutionary Biology, Harvard University, 02138, Cambridge, Massachusetts, U.S.A.
- 3) Department of Population Biology, Research School of Biological Sciences, Australian National University, Canberra, A.C.T., Australia
The chromosomes of Crocodylus porosus, C. johnstoni and Caiman crocodilus have been analysed using C, G and N-banding techniques and the in situ hybridization of 18S+26S rRNA cistrons derived from Xenopus. It is clear that in addition to the gross structural changes (robertsonian rearrangements and pericentric inversions) which are known to distinguish these crocodiles, numerous other modes of repatterning have occurred. These involved both the heterochromatic and euchromatic portions of the genome. They appear to be associated with the gross structural changes which have been established, and involve two distinct forms of chromatin transformation. In addition, the in situ hybridization of 18S+26S rRNA cistrons onto these crocodilian chromosomes has localized the site of nucleolus organizer activity to the C-band positive G-band negative secondary constrictions present in all three species. The significance of these results is discussed.
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