ANALYSIS OF VNTR LOCI IN FISH GENOMES USING SYNTHETIC OLIGODEOXYRIBONUCLEOTIDE PROBES

A set of synthetic oligodeoxyribonucleotide (oligo) probes, OAT18, OMS 1 and OAT24 carrying the (TGG)(6), (GGAT)(4) and (GACA)(6) repeat moti fs, respectively, was used to analyze the variable number tandem repea t (VNTR) loci in the genomes of Oncorhyncus mykiss (rainbow trout; fam ily Salmonidae), Oreochromis mossambicus and Oreochromis niloticus (bo th tilapia belonging to family Cichlidae). Of all the oligos and enzym es (AluI, MboI, HaeIII and Hinfl) used, the OAT18/HaeIII combination w as found to be most informative for detecting DNA fingerprinting in ra inbow trout, while the OMS1/MboI combination gave the most informative pattern for the Or. niloticus genome. In the rainbow trout genome, al l three repeat loci were hypervariable, revealing varying degrees of p olymorphism as compared to tilapia genomes. Startlingly, the OAT24 pro be did not cross-hybridize with Or. mossambicus and lamprey salmon (La mpetra japonica) although GACA repeats have been reported to be evolut ionarily conserved in all eukaryotes studied thus far. Cluster analysi s with respect to GGAT repeat loci revealed that Or. niloticus diverge d from Or. mossambicus before the separation of On. mykiss, suggesting the relatively recent evolution of these loci in rainbow trout, compa red to the tilapia genomes. These highly informative probes will find application in various genetic studies of fishes.