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Dendrogram of 655 HIV-1 sequences depicting the maximal relative relationship to one another (Los Alamos database and data from the Swiss HIV Cohort Study). Blue letters, R5-tropic viruses; red letters, X4-tropic isolates. Lobes of related sequences correspond with subtypes/groups (capital letters); the group O branch with 4 isolates is truncated. Yellow arrow indicates arbitrary reference sequence HIV-1JR-CSF.
