Lysis plaques of lambda phage on E. coli bacteria.

Lysis plaques of lambda phage on E. coli bacteria.

By itself a viral particle is just an amalgamation of macromolecules: genetic material in the form of either DNA or RNA, a protein capsid, and in some cases a lipid envelope. A virus has no metabolism. It is an inert particle. However, when a virus infects a host organism it can make use of the host cell's components and metabolism to produce multiple copies of itself, which assemble in the cell. Although the life cycle of viruses can differ greatly among species, there is a general common narrative involving attachment, penetration, uncoating, replication, assembly and release.

There are many examples of human diseases caused by viruses including the common cold, influenza, chickenpox, Ebola and AIDS. For future doctors, the basic microbiology of viruses is an obvious focus. From life cycle to classification, the details of viruses must be well reviewed before the MCAT. Additionally, certain viruses are valuable tools as vectors in recombinant DNA experiments, so there is an additional aspect to study which is the important role viruses play in the molecular biology laboratory.

WikiPremed Resources

Learning Goals


Be able to describe the basic components of a virus.

Be prepared to distinguish the various types of virus using the Baltimore classification system.

Be able to narrate the stages of the infective cycle of DNA bacteriophages.

Be able to distinguish the infective cycles of negative from positive strand RNA viruses.

Understand the infective cycle of retroviruses.

Understand the difference between lytic and latent infections.

Be able to describe how viruses may be used as vectors in recombinant DNA experiments.

Be familiar with subviral particles prions and viroids and models proposed for their replication.

Suggested Assignments

Review the terminology for viruses using the question server. Complete the fundamental terms crossword puzzle. Here is the solution to the puzzle.

Read pp. 1-13 in ExamKrackers Biology II. Perform practice items 1-8 on pg. 14. (This section has treatments of evolution as well as viruses and bacteria).

Review the web resources for viruses.

Conceptual Vocabulary for Viruses