Which option is NOT one of the two basic structures of viruses?

Which option is NOT one of the two basic structures of viruses?

• A. Hollow rod-shaped threads and hollow polyhedrons
• B. Helical and icosahedral
• C. Filamentous and spherical
• D. Capsid and envelope

Answer: (D)

Viruses are classified by the shape of their protective shell around the genome into two main forms: helical and icosahedral. The capsid is that protein coat, and in some viruses an outer envelope derived from the host cell’s membrane may surround that capsid. The option listing capsid and envelope names components rather than a single structural form, so it does not describe one of the two basic morphologies. The other choices describe rod-like or filamentous shapes and polyhedral or spherical shapes, which are examples of the structural forms. Hence, capsid and envelope is not one of the two basic structures.

Viruses are classified by the shape of their protective shell around the genome into two main forms: helical and icosahedral. The capsid is that protein coat, and in some viruses an outer envelope derived from the host cell’s membrane may surround that capsid. The option listing capsid and envelope names components rather than a single structural form, so it does not describe one of the two basic morphologies. The other choices describe rod-like or filamentous shapes and polyhedral or spherical shapes, which are examples of the structural forms. Hence, capsid and envelope is not one of the two basic structures.