Amplification and direct sequencing of fungal ribosomal RNA genes for phylogenetics
Comparative studies of the nucleotide sequences of ribosomal RNA (rRNA) genes provide a means for analyzing phylogenetic relation ships over a wide range of taxonomic levels (Woese and Olsen 1986; Zimmer et al 1988; Medlin et al 1988; Jorgensen and Cluster 1989). The nuclear small-subunit rDNA sequences (16S-like) evolve rela tively slowly and are useful for studying distantly related organisms, whereas the mitochondrial rRNA genes evolve more rapidly and can be useful at the ordinal or family level. The internal transcribed spacer region and intergenic spacer of the nuclear rRNA repeat units evolve fastest and may vary among species within a genus or among populations. Numerous sequences of rRNA genes have been obtained primarily by isolating and sequencing individual cloned genes (Medlin et al 1988). Direct rRNA sequencing (Lane et al 1985) has also been used to rapidly obtain sequence data.
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