All HPV-6 and HPV-11 isolates share common L1 DNA sequences. Fig. 3 upper HPV-6 DNA isolate from a clinical sample with its partial L1 gene DNA sequence of 50 bases is validated as HPV-6 by the GenBak database. Fig. 3 lower HPV-11 DNA isolate from a clinical sample with its partial L1 gene DNA sequence of 50 bases is validated as HPV-11 isolate Bsb-45 major capsid protein by the GenBak database. From the left No. 4 base onward (upstream), all known HPV-6 (upper) and HPV-11 (lower) isolates share a 34-base sequence. In this "hypervariable region" which is generally used for HPV L1 genotyping, differentiation between HPV-6 and HPV-11 depends on identification of a four-base difference upstream of these 34 common bases, but before another sequence homogeny starting with CCCCA.