The key to numerical taxonomy is that no one trait eg

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Unformatted text preview: ristics. The key to numerical taxonomy is that no one trait (e.g., ability to ferment glucose) is elevated in importance above any other trait (e.g., Gram staining characteristics). Instead, all traits are weighted equally. Classification in numerical taxonomy is expressed in terms of a Similarity Coefficient found between two compared strains. It is equal to: [# pos both strains]/[# pos one or both strains] by “pos” I mean that the characteristic is present, e.g., ferments glucose or has pili, etc. Greater similarity coefficient, closer relatedness is inferred. Greater than ~70% and inference is that two compared bacteria are of the same species. dsDNA is distinguished from ssDNA based on UV absorbance. Different species have different DNA melting temps. DNA-DNA Hybridization Helix has higher stability with greater fraction GC vs. A-T pairing. Higher melting points therefore correspond to greater G-C content 5 Similarity is in terms of nucleotide sequence between the two compared organisms. 16S rRNA Sequence Comparison DNA-DNA Hybridization 16S rRNA Link to Next Presentation 6 DNA-DNA Hybridization 10...
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