1994. Organization of microsatellites differs between mammals and cold-water teleost fishes. Can. 8 . Fish. Aquat. Sci. 51 : 1959-1 966. Microsatellites, in particular (dG-dT), and (dG-dA), dinucleotide repeats, are abundant and display a high degree of length polymorphism and heterozygssity in eukaryotic gewomes. Here, we report the cloning and characterization of 64 microsatellite sequences from Atlantic cod, Gadus moshua. The microsateiBites were classified as perfect, imperfect, and compound repeats. The length and integrity of these repeats were compared with rnicrosatellites characterized from two other teleosts, rainbow trout (Oncorhynchus mykiss) and Atlantic salmon (Salmo salar), and from three mammalian genomes, human, porcine, and canine. Differences were found in the proportions of the repeat classes; however, the most significant difference between rnicrosatellites from teleost fishes and mammals was the propensity of the former to be of greater length: some cod and rainbow trout rnicrosatellites were more than twice the size of the longest microsatellite repeats reported for any mammalian genome. Primers for PCR amplification were constructed for seven of the cod rnicrosatellites. Allele frequencies, degree of polymorphism, and heterozygosity were estimated for a sample population. Amplification with these cod primers was also carried out on a number of related gadids. These polymorphic microsatellite loci have enormous potential utility as genetic markers for use in population, breeding, and evolutionary studies.kes chaines dlADN microsatellite, et plus particuliitrement les sequences repktitives des dinuclbotides (dG-dT),et (dC-dA),, sont abowdantes et Beurs genornes eucaryotes presentent un taux blev6 de polymorphisrne et d'hbtkrozygositk. Dans ce rapport, nous presentons les resultats du clonage et de la caractkrisation de 6Q sequences dfADN microsatellite de la rnorue franche, Gadus rnsrhua. kes ADN rnicrosatellites ktaient classees en trois categories : parfaites, irnparfaites et 3 sequence de repetition cornposke. La longueur et I'intkgritb de ces sequences de rkpetition ont 6te comparees a celles dtADN microsatellite caractbrisee chez deux autres tkl6ostbens, la truite arc-en-ciel (Oncorhynchus mykiss) et le saumon de I'Atlantique (Salrno salar), et chez trois gknomes de mamrnif$res, (hurnain, porcin et canin). On a trouve des differences dans les proportions des categories de sequences de repetition; toutefois, la difference la plus significative entre les ADN microsatellites de t6leosteens et celle de mammif5res etait kmne tendance 5 une longueur superieure chez ces derniers : les ABN microsatellites de certaines morues et truites arcen-ciel etaient deux fois plus Bongues que les skquences repktees d'ADN microsatellite observkes pour tous les genomes de mammiferes. Des amorces pour Itamplification par la PCR ont et6 crkkes pour sept des ADN microsatellites de morue. kes frbquences d'alleles, le degre de polymorphisme et 11het6romygosit6 ont et6 estimks pour une population kchantillon. On a...

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