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Patent Pending HIV-1 is the most common and pathogenic strain of the virus. Scientists divide HIV-1 into a major group (Group M) and two or more minor groups. Each group is believed to represent an independent transmission of SIV into humans (but subtypes within a group are not).[2] A total of 39 ORFs are found in all six possible reading frames (RFs) of HIV-1 complete genome sequence,[3] but only a few of them are functional.