General Characteristics of Viruses

• Viral structure: Typical viral components are shown in Fig. 2. These components are a nucleic acid core and a surrounding protein coat called a capsid. In addition some viruses have a surrounding lipid bilayer membrane called an envelope.

Fig. 2. The components of helical virus

A. Nucleic acid

• Viral genomes are either DNA or RNA (not both)

• Nucleic acid may be single- or double-stranded

Fig. 3. Types of virus genomes

B. Capsid

• protein coat
• Protection of Nucleic Acid
• Provides Specificity for Attachment
• Capsomeres are subunits of the capsid

Fig. 4. Capsid structure