Final answer:
HCV, Dengue, and Zika viruses are characterized by having single-stranded RNA genomes, which allow their RNA to be used directly as messenger RNA for protein synthesis in host cells.
Step-by-step explanation:
HCV (Hepatitis C Virus), Dengue, and Zika viruses all contain single-stranded RNA genomes. Viral genomes vary widely, and although some viruses have DNA genomes, these particular viruses do not. RNA viruses can have single or double-stranded genomes, but in the case of these three viruses, they all have single-stranded RNA (ssRNA) genomes with positive polarity, which means the RNA can serve directly as mRNA.
This configuration allows the RNA to be immediately translated into proteins following infection of a host cell. For HCV, which belongs to the family Flaviviridae, as well as Dengue and Zika viruses that are also part of the same family, their ssRNA genome is characteristic of Group IV viruses according to the Baltimore classification scheme. So, these viruses use their ssRNA not just for encoding genetic information but also as a template for replication and for immediate protein synthesis within the host cells.