Microbial genetics

 Microbial genetics studies how microorganisms like bacteria and viruses inherit and express genetic information. Because they lack a nucleus, these processes often occur simultaneously in the cytoplasm. [1, 2, 3]

1. The Central Dogma (Flow of Information)

In microbes, genetic information flows from DNA to RNA to protein. [4]
  • Replication: The bacterial chromosome (and plasmids) is copied so each daughter cell gets a complete set of instructions.
  • Transcription: An enzyme called RNA polymerase reads a DNA segment (a gene) to create a matching strand of mRNA.
  • Translation: Ribosomes read the mRNA to build a specific protein. In bacteria, ribosomes often begin translating the mRNA while it is still being transcribed.

2. Horizontal Gene Transfer (HGT)

Unlike animals, which only pass genes to offspring, bacteria can swap genes with their "peers" through three main methods: 
Mechanism DescriptionKey Feature
TransformationA cell picks up free-floating "naked" DNA from the environment.Requires a "competent" state.
TransductionA virus (bacteriophage) accidentally carries bacterial DNA from one host to another.Mediated by viruses.
ConjugationTwo bacteria connect via a sex pilus to transfer a copy of a plasmid.Direct cell-to-cell contact.

3. Genetic Regulation: The Operon Model

Microbes are highly efficient and only make proteins when they need them. The Operon Model explains this. [2, 17, 18]
  • Promoter: Where RNA polymerase binds to start.
  • Operator: The "on/off switch" where a repressor protein can block transcription.
  • Structural Genes: The actual blueprints for proteins (e.g., the lac operon for digesting lactose). 


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