Possible role of RNA-dependent DNA-polymerase in early stages of evolution.

The tDNA cistrons have permuted sequences of triplets corresponding to anti-codons in tRNA at specific regions in their sequences. We invoke reverse transcription for the generation of such sequences in the genome during early stages of evolution. Making the assumption that a single tDNA cistron, in a genome might have come into existence by an 'accident', after transcription, tRNA is expected to fold into a three-dimensional shape analogous to the contemporary tRNA, where the anti-codon triplet bases are sticking out well-exposed for chemical mutagens. The mutated tRNAs would have been reverse-transcribed into the genome by crude analogs of now-known reverse-transcriptases. The back and forth process of transcription and reverse transcription would give rise to all the tDNA cistrons with the required anti-codons. This process may act as an important feedback mechanism for the efficient progress of evolution.