🦠microbiology review

Baltimore classification system

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

The Baltimore classification system categorizes viruses based on their type of genome and their method of replication. It includes seven classes, each defined by whether the viral genome is DNA or RNA, single-stranded or double-stranded, and how it replicates.

5 Must Know Facts For Your Next Test

  1. There are seven classes in the Baltimore classification system.
  2. Class I includes double-stranded DNA viruses like Herpesviruses.
  3. Class IV contains positive-sense single-stranded RNA viruses such as the Poliovirus.
  4. Reverse transcription is a key feature for Class VI and VII viruses, which include Retroviruses like HIV.
  5. Each class represents a different approach to mRNA synthesis and replication.

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