Chapter 8

Oct 4, 2024

Lecture 9: Microbial Genetics - Chapter 8

Administrative Details

  • Date: Monday, September 30th
  • Lecture Number: 9
  • Attendance Code: 444
  • Word of the Day: Genes
  • Exam 1 due by October 3rd, 5:00 PM
  • Assignment 5 due this Friday
  • Late assignment submissions must be communicated via Canvas
  • Lowest exam score of the four exams will be dropped

Upcoming Topics

  • Survey of the Microbial World
    • Prokaryotic cells
    • Eukaryotic microbes
    • Microbial ecology
    • Food microbiology (Chapter 28)

Microbial Genetics: Key Concepts

Key Terms

  • Genes: Segments of DNA that encode functional products, usually proteins
  • Genetics: Study of genes, their information, and replication
  • Chromosomes: Main DNA-containing structures in a cell
  • Genome: All genetic information in a cell or virus
  • Genomics: Study of genomes

Genetic Code

  • Rules for converting nucleotide sequences to amino acids
  • Central Dogma: DNA -> RNA -> Protein
    • Some viruses break this rule

DNA and RNA

  • DNA: Double-stranded, nucleotides A, T, G, C
  • RNA: Single-stranded, uracil (U) replaces thymine (T)
  • Amino acids coded by three nucleotides

Genotype vs. Phenotype

  • Genotype: Genetic makeup
  • Phenotype: Expression of genes

DNA Replication

  • Replication Fork: Area where two strands of DNA separate
  • Leading Strand: Synthesized continuously
  • Lagging Strand: Synthesized in Okazaki fragments
  • DNA Polymerase: Adds nucleotides
  • DNA is read and synthesized from 5' to 3'

Bacterial DNA Replication

  • Semiconservative: New DNA has one parent and one daughter strand

RNA Synthesis - Transcription

  • Occurs from DNA to RNA
  • Types: rRNA, tRNA, mRNA
  • Promoter: Start sequence for RNA polymerase
  • Terminator: Stop sequence

Translation

  • mRNA translation to protein starts at AUG
  • TRNA: Carries amino acids to ribosomes

Gene Regulation

Operons

  • Clusters of genes with related functions
  • Constitutive Genes: Always on
  • Inducible Genes: Normally off, can be turned on
  • Repressible Genes: Normally on, can be turned off

Catabolite Repression

  • Glucose preferred; other pathways repressed
  • Camp: Builds up when glucose is low, initiating lactose use

Epigenetic and Post-Transcriptional Control

  • Epigenetics: Turning genes on/off via methylation
  • Riboswitches: Regulate mRNA translation
  • Micro RNAs: Inhibit translation by creating double-stranded RNA

Mutations

  • Point Mutation: Change in single nucleotide
    • Silent, missense, nonsense
  • Frameshift Mutation: Insertion or deletion causing a shift

Genetic Diversity

  • Recombination: Exchange of genetic material
    • Vertical: Parent to offspring
    • Horizontal: Transfer between same generation

Plasmids and Conjugation

  • Plasmid: Extrachromosomal DNA, self-replicating
  • Conjugation: Gene transfer via cell-to-cell contact
    • F+ cells: Donors
    • HFR cells: High frequency of recombination

Transposons and Transduction

  • Transposons: Movable pieces of DNA
  • Transduction: Gene transfer via bacteriophage

Study Tips

  • Read textbook before class
  • Review notes after class
  • Form study groups
  • Utilize office hours for questions

This concludes Lecture 9 on Microbial Genetics. Please prepare for the upcoming material and reach out if you have further questions during office hours.