FIG. 7.

Mechanisms for vDNA terminal truncations. (A) The path on the left shows how the termini become truncated after complete synthesis of the vDNA by unabated reverse transcription. Exonuclease degradation of the double-stranded vDNA (ds vDNA) would account for the missing nucleotides at the vDNA termini. (B) The scheme on the right shows how incomplete synthesis of vDNA could occur, due to the inability of NC to completely melt the double-stranded vDNA complementary regions, U3|R|U5 and PBS, thus blocking RT from completing synthesis to the proper ends. Nucleases would then degrade single-stranded vDNA overhangs (ss vDNA).