retrovirus

any of a group of viruses that contain two single-strand linear RNA molecules per virion and reverse transcriptase (RNA to DNA); the virus transcribes its RNA into a cDNA provirus that is then incorporated into the host cell

ビリオンあたり2本の単鎖線状RNA分子と逆転写酵素（RNAからDNA）を含むウイルスの総称；自身のRNAをcDNAプロウイルスへと転写し、それが宿主細胞に組み込まれる