Recently published evidence for sequence repetition in polyvirus genom
es prompted us to analyse the published complete genome sequences and
coat protein gene sequences of viruses of this family for evidence of
replication slippage. Five of nine complete genomic sequences and 17 o
f 32 coat protein genes had significant sequence repetitions. Most of
these were in coat protein genes, although the 5' region of the turnip
mosaic virus genome also showed evidence of slippage. The results sug
gest that replication slippage may be involved in the evolution of vir
uses, as well as prokaryotes and eukaryotes, and that slippage can occ
ur in both RNA and DNA when it is being replicated.