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.