The Molecular Genetics of Viruses

Rucete ✏ Biology In a Nutshell

1. Structure of Viruses

• Nucleic Acid: The genetic material of a virus can be either DNA or RNA, single- or double-stranded. It contains the virus’s hereditary information.
• Capsid: A protein coat that surrounds and protects the nucleic acid.
• Capsomeres: Individual protein subunits that make up the capsid.
• Envelope (in some viruses): A lipid membrane derived from the host cell, embedded with viral proteins.

2. Replication of Viruses

a) Lytic Cycle

• Virus attaches to the host cell and injects its genetic material.
• Viral DNA or RNA directs the host to make viral proteins and nucleic acids.
• New viruses are assembled inside the host.
• The host cell bursts (lysis), releasing new viruses to infect other cells.

b) Lysogenic Cycle

• Viral DNA becomes integrated into the host cell’s DNA, forming a provirus.
• The viral DNA is replicated along with the host DNA during cell division.
• The virus remains dormant until triggered to enter the lytic cycle.