Potential for variability through multiple gene products of bacteriophage phiX174.

The small single-stranded DNA phages phiX174 and S13 produce multiple products of certain phage genes, as observed by electrophoresis on SDS-polyacrylamide slab gels. Two A protein products, two A products and four G products are observed. The multiple gene products may arise from multiple sites for initiation or termination of translation, or by protein modification. Some of the variant products may provide a substitute for heterozygosity without a concomitant increase in the size of the genome.