Chapter 8: Microbial Genetics

Microbial Genetics introduces the central dogma of molecular biology, where DNA is transcribed into RNA, which is then translated into protein. The structure of DNA is reviewed, emphasizing complementary base pairing and antiparallel strands, and the process of DNA replication is described as semi-conservative and mediated by enzymes like DNA polymerase, helicase, and ligase. Next, the chapter details transcription and translation in prokaryotes, explaining how mRNA, rRNA, and tRNA function in protein synthesis. It covers codons, the genetic code, and how ribosomes read mRNA to produce polypeptides. Gene regulation is explored through the operon model, particularly the lac operon, which exemplifies inducible gene expression, and the trp operon for repressible systems. The chapter then turns to mutations—changes in DNA sequence—including base substitutions, frameshift mutations, and their potential effects. It distinguishes between spontaneous and induced mutations and discusses mutagens like radiation and chemicals. DNA repair mechanisms, such as photolyase and nucleotide excision repair, are also introduced. A major focus is placed on genetic recombination in bacteria. Transformation (uptake of naked DNA), conjugation (plasmid transfer via sex pili), and transduction (DNA transfer via bacteriophages) are all examined as methods of horizontal gene transfer. The chapter emphasizes the role of plasmids—like R factors and F factors—in spreading antibiotic resistance and other traits. Transposons, or “jumping genes,” are introduced as mobile genetic elements that can insert themselves within genomes. Finally, the chapter links microbial genetics to biotechnology and public health, highlighting how understanding gene transfer mechanisms enables innovations like genetic engineering, gene cloning, and the fight against antibiotic resistance.