Problem :
What are two characteristics by which viruses are classified?
Viruses are classified according to the type of genetic material they have and
by the shape of their capsid.
Problem :
What types of genetic material might a virus carry?
Viruses are known to carry single-stranded and double-stranded DNA and single-
stranded and double-stranded RNA. The molecules may be linear or circular.
Problem :
What are the two main types of capsid shape?
Capsids may be helical (tube-like) or icosahedral (ball-like).