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Explore bacterial genetics concepts from Chapter 8, including gene expression methods, mutations, DNA acquisition, and repair processes. Dive deeper into understanding natural selection and evolution in bacteria.

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Announcements

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  1. Announcements • You must go and check your plates today! • Ch. 8 Part 1 homework is due Monday • Remember how to submit it if you miss class • Friend • Scan and email it • Put in box…Just make sure it is BEFORE class ends (if it’s not in there by 10 AM then a “0”)

  2. Bacterial GeneticsChapter 8 Part 1

  3. Think-Pair-Share Question (2 Mins) Bacteria use 2 methods to change their gene expression, what are they? Hint: 1 you know in detail Answer: 1. Regulating Gene Expression deliberate, intentional! (Ch.7) 2. Genetic Change via mutations (this is random!) or acquiring DNA from another bacteria (horizontal gene transfer)

  4. Think-Pair-Share Question (2 Mins) Which statement is correct? • Natural selection and evolution drive mutations. • Random mutations that lead to better survival/reproduction are acted on by natural selection. MISCONCEPTION!!

  5. Based On The Correct Understanding Of Natural Selection… For a bacterium, did the genetic change happen first that became an advantage for survival -or- does the need for better survival drive the formation of genetic change?

  6. The Point: Change Then Natural Selection Based on Environment Not the Other Way Around! • Mutations and acquiring DNA is random • If it leads to better survival and there is a need for that variant (because of some factor) then those will be selected for (passed on)! Environmental Change Random Mutation Pass the mutation on! Natural Selection

  7. Let’s Review • Genotype: the set of genes an organism carries • Again, the name gives it away: geno=gene • Phenotypes: organism’s appearance Phenotype ahpC lacZ lacA Genotype

  8. Two Ways To Get Mutations • Spontaneously • Result from normal processes • 3 types • Rate that this occurs for a gene is 1 in 10,000 to 1 in a trillion • Can a mutation go back to the original form? rare, but it does happen: reversion • Question: Are 2 mutations likely? Incredibly Rare Event! • How do you know? • Induced • Occur by external forces: chemicals, radiation

  9. Spontaneous Mutations: Base Substitution • If one base is changed-point mutation

  10. Spontaneous Mutations: Base Substitution Outcomes

  11. Spontaneous Mutations: Deletion or Addition of Bases • Causes a frameshift mutation

  12. Spontaneous Mutations: Transposons

  13. Induced Mutations: Chemicals (Alkylating Agents)

  14. Induced Mutations: Chemicals (Base Analogs)

  15. Induced Mutations: Chemicals (Intercalating Agents) • Cause a frameshift mutation • Used in lab settings to stain DNA

  16. Induced Mutations: Chemicals (UV Light) • Distorts DNA • Cell dies if damage cannot be repaired

  17. How do cells repair the damage caused spontaneously and or induced by chemicals or radiation?

  18. Spontaneous Mutation Repair: Mismatch Repair

  19. Induced Mutations: UV Light Repair

  20. Induced Mutations: UV Light Repair Cont. • SOS Repair-Last ditch effort to repair DNA • Do you know what SOS stands for? • Normal DNA polymerase stalls when it gets to areas of extensive damage • But if the SOS system has been activated, a special DNA polymerase can replicate DNA even if it is highly damaged

  21. Why are correcting mutations important? • For microbes, mutations that lead to alterations in DNA replication, protein expression and function can result in death • For humans and animals, if you don’t correct mutations you can get cancer

  22. Let’s Work a Problem Together…

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