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”)

Bacterial GeneticsChapter 8 Part 1

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)

Think-Pair-Share Question (2 Mins)

Which statement is correct?

1) Natural selection and evolution drive mutations.

2) Random mutations that lead to better survival/reproduction are acted on by natural

selection.

MISCONCEPTION!!

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?

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)!

Random Mutation Environmental ChangePass the mutation on!

Natural Selection

Let’s Review

• Genotype: the set of genes an organism carries– Again, the name gives it away: geno=gene

• Phenotypes: organism’s appearance

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Genotype

Phenotype

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

Spontaneous Mutations: Base Substitution

• If one base is changed-point mutation

Spontaneous Mutations: Base Substitution Outcomes

Spontaneous Mutations: Deletion or Addition of Bases

• Causes a frameshift mutation

Spontaneous Mutations: Transposons

Induced Mutations: Chemicals (Alkylating Agents)

Induced Mutations: Chemicals (Base Analogs)

Induced Mutations: Chemicals (Intercalating Agents)

• Cause a frameshift mutation• Used in lab settings to stain DNA

• Distorts DNA• Cell dies if damage cannot be repaired

Induced Mutations: Chemicals (UV Light)

How do cells repair the damage caused spontaneously and or induced by chemicals or

radiation?

Spontaneous Mutation Repair: Mismatch Repair

Induced Mutations: UV Light Repair

• 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

Induced Mutations: UV Light Repair Cont.

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

Let’s Work a Problem Together…