For a typical virus, the lifecycle can be divided into five broad steps: attachment, entry, genome replication and gene expression, assembly, release.
In everyday life, we tend to think of a viral infection as the nasty collection of symptoms we get when we catch a virus, such as the flu or the chickenpox. At the microscopic scale, a viral infection means that many viruses are using your cells to make more copies of themselves. The viral lifecycle is the set of steps in which a virus recognizes and enters a host cell, “reprograms” the host by providing instructions in the form of viral DNA or RNA, and uses the host’s resources to make more virus particles (the output of the viral “program”).
For a typical virus, their lifecycle can be divided into five broad steps (though the details of these steps will be different for each virus):
- Attachment: The virus recognizes and binds to a host cell via a receptor molecule on the cell surface.
- Entry: The virus or its genetic material enters the cell.
- Genome replication and gene expression: The viral genome is copied, and its genes are expressed to make viral proteins.
- Assembly: New viral particles are assembled from the genome copies and viral proteins using the host cell ribosomes
- Release: Completed viral particles exit the cell and can infect other cells.
Practice Questions
MCAT Official Prep (AAMC)
Biology Question Pack, Vol 2. Passage 8 Question 53
Biology Question Pack, Vol 2. Passage 8 Question 54
Biology Question Pack, Vol 2. Passage 9 Question 59
Biology Question Pack, Vol 2. Passage 9 Question 60
Biology Question Pack, Vol 2. Question 101
Key Points
• For a typical virus, the lifecycle can be divided into five broad steps: attachment, entry, genome replication and gene expression, assembly, release.
Key Terms
Genome: the whole of an organisms hereditary information encoded in its DNA
Ribosomes: organelles that carry out protein synthesis
RNA: is a single-stranded RNA molecule that is read by a ribosome to produce a protein
