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.