| 
      For both HepG2 and CCD-1112Sk cells, the frequency of mutations was higher for
        |   | HepG2 AZT- | HepG2 AZT+ | CCD-1112Sk AZT- | CCD-1112Sk AZT+ |  
        | HV2 | 2.2x10-5 | 4.2x10-5 | 1.4x10-5 | 4.3x10-5 |  
        | CO2 | 1.4x10-5 | 3.1x10-5 | 3.3x10-5 | 4.4x10-5 |  
        | ND1 | 2.9x10-5 | 5.2x10-5 | 1.6x10-5 | 3.4x10-5 |  the AZT treated samples.
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