Genome in virion Viral genomes. The genomes of viruses can be composed of either DNA or RNA, and some use both as their genomic material at different stages in their life cycle. However , only one type of nucleic acid is found in the virion of any particular type of virus. This can be single￾stranded (ss), double-stranded (ds), or in the case of the hepadnaviruses, partially double-stranded.Genome in virion Viral genomes. The genomes of viruses can be composed of either DNA or RNA, and some use both as their genomic material at different stages in their life cycle. However , only one type of nucleic acid is found in the virion of any particular type of virus. This can be single￾stranded (ss), double-stranded (ds), or in the case of the hepadnaviruses, partially double-stranded