Final answer:
The three primary criteria for classifying virus families are genetic makeup, structure such as capsid design and presence of an envelope, and the specific cell type the virus infects.
Step-by-step explanation:
The three main criteria used in classifying virus families are genetic makeup, structure, and the cell type infected. Geographic distribution and chemical composition, while relevant to viral studies, are not primary criteria for classification.
Viruses are incredibly small and diverse entities that infect a broad range of host organisms. The classification of viruses is based on specific characteristics essential for understanding their biology and for developing targeted treatments. The genetic makeup of a virus includes whether it contains DNA or RNA, and if it is single or double-stranded, linear or circular, and segmented or non-segmented. The structure of viruses refers to the design of their capsids, which can be icosahedral, helical, or complex, and whether they have an outer envelope. Lastly, classification takes into account the cell type infected by the virus, which defines host range and tissue specificity. The Baltimore classification system is a widely used method that categorizes viruses based on how they replicate and produce their messenger RNA (mRNA).
The distinctions in these categories allow scientists to organize viruses systematically and tailor medical responses to the unique challenges each virus presents.