Fig. 1.

Schematic of DGR. Genetic information is transferred from an invariant TR to the VR of a variable protein (in this case AvpA), requiring the action of a reverse transcriptase (RT) and an accessory variability determinant (Avd) protein. This process involves reverse transcription of an RNA encoding the TR, and is accompanied by adenine-specific mutagenesis of the TR sequence. The mutagenized cDNA homes to the variable protein locus, and replaces the sequence information in the VR, resulting in a variant of the variable protein