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21.
DNA sequences of an intergenic spacer (IGS) and parts of genes in the nif cluster were amplified by the polymerase chain reaction (PCR) using two primers derived from nifD -and nifK -conserved sequences. The PCR products were cleaved by ten 4–base cutting restriction enzymes and the restriction patterns were used as fingerprints to type Frankia strains. The feasability of this PCR-RFLP method for typing Frankia strains was investigated on Frankia reference strains belonging mainly to the Elaeagnaceae infectivity group but also on new Frankia isolates and on other N2 -fixing microorganisms. By modulating the stringency of the amplifications, we showed the method allowed to target either Frankia strains or the whole N2 -fixing microbial community. DNA digestion patterns were used to estimate the sequence divergence between the Frankia nifD-K fragment. The estimated relationships deduced from these genotypic data correlated well with established Frankia taxonomic schemes. 相似文献
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OSVALDO A. REIG F.L.S SPOTORNO O. ANGEL † FERNANDEZ D. RAUL † 《Biological journal of the Linnean Society. Linnean Society of London》1972,4(1):29-38
Chromosomes obtained from bone-marrow, spleen and testes were studied in samples from five populations of Spalacopus cyanus of Central Chile. Animals of four low-land coastal localities and animals of a high Andean valley showed a karyotype of 2n = 58 chromosomes, with almost no variation, either in number or in structure, both within each population or among the various populations. This karyotype was found to be very similar to that of Octodon degus , but very different to those in species of Ctenomys. The evolutionary and systematic significance of these results is discussed. The lack of karyotypic variation found in Spalacopus is correlated with its taxonomic uniformity, and both could be the result of the high vagility of the populations of this rodent, suggested by previous studies. This high capacity of dispersal is supposed to have enhanced gene flow, and therewith chromosome uniformity and low taxonomic diversification. The occurrence of a case of dimorphism for the presence of a secondary constriction in one of the autosome pairs is reported and discussed. 相似文献
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