Transcript Germs, Drugs, and Genes (PowerPoint) West Coast 2013

Group 6
GERMS, DRUGS and GENES:
Revealing mechanisms of gene expression
using antibiotics
Alejandro Calderon-Urrea
Nancy Connell
Nigel Crawford
Mamta Rawat
Ella Tour
Facilitator: Ken Burtis
Level: Lower Division Biology Class for Majors
Learning Goals:
1. The student will be able to understand how genotype
determines phenotype.
2. The student will identify steps in gene expression and
how some drugs affect different levels of gene
expression.
Learning Outcomes
1. The student will find and illustrate the
mechanisms of action of certain antibiotics and
relate these actions of antibiotics to steps in gene
expression.
2. The student will be able to explain how resistance
to antibiotics arises from a change in the genetic
material of the cell.
3. The student will be able to apply principles of
antibiotic resistance in bacteria to drug resistance
in eukaryotic cells.
4. The student will propose strategies for the
development of new drugs.
GENOTYPE
?
PHENOTYPE
GENOTYPE
Antibiotics
PHENOTYPE (DEATH)
Internet search (2 minutes)
Pair up and pick one of the following antibiotics. Each
pair search the internet and find out about the target of
the antibiotic (each group covers all three antibiotics).
1. Ciprofloxacin (cipro)
2. Rifampicin (rifampin)
3. Tetracycline
Group share and drawing exercise (3 min)
Draw a bacterial cell on poster paper and illustrate
the targets of antibiotics.
Mechanisms of action of three antibiotics
Tetracycline
Translation
Ribosome
DNA
replication
Gyrase
Transcription
RNA
Pol
Ciprofloxacin Rifampicin
Clicker question (2 min)
How do antibiotics become ineffective against bacterial
infection?
A. Human body develops mechanisms to inactivate the antibiotic.
B. Treating bacteria with antibiotics changes their physiology so
they become resistant
C. The antibiotic causes the mutation in the bacteria which leads
to resistance
D. Existing mutants in the bacterial population that are already
resistant to the antibiotic are selected and proliferate
E. All of the above
In class: Peer instruction (Vote, Think pair share, Re-vote)
followed by discussion of different options by instructor
Genotype 1
Phenotype 1:
Susceptibility
Genotype 2
Phenotype 2:
Resistance
Nancy
http://www.niaid.nih.gov/topics/antimicrobialResistance/
Nancy
http://www.niaid.nih.gov/topics/antimicrobialResistance/
Nancy
Genotype 1
Phenotype 1:
Susceptibility
Genotype 2
Phenotype 2:
Resistance
Ella
We have learned that resistance arises in populations
by mutation or acquisition of new genes.
How could a mutation lead to antibiotic resistance?
Propose mechanisms or targets in bacteria that could
be altered to produce resistance.
Group share
Use the internet to find mechanisms of resistance for
your antibiotic.
Report to group. Use your drawings to illustrate what
you found.
“Call out” three groups for each antibiotic. (skip)
1. Ciprofloxacin (cipro)
2. Rifampicin (rifampin)
3. Tetracycline
Can you think of an instance in which eukaryotic cells
acquire resistance to drugs or chemicals?
Group share.
Report out.
Homework
A patient is undergoing cancer treatment with an anti-cancer
drug. For a while, the cancer is responding and the tumor is
shrinking significantly. However, after 6 months, the cancer
comes back: the tumor cells continue to proliferate even when
the dosage of the drug is increased.
A. Based on what you've learned today, suggest two possible
mechanisms that allowed the cancer cells to become resistant to
the drug.
B. You wish to find a new drug to treat this cancer. What process
or molecule in these resistant tumor cells would you propose to
target in your new drug study?
The answers will be discussed next class.
Pre-test/Post-test
1. Explain how genetic information is transferred from DNA to RNA to
proteins. Include the terms: DNA replication, transcription,
translation. (LOC)
2. What could be the consequences to this flow of information if a
mistake occurs during DNA replication? (LOC/HOC)
3. Describe four examples of mechanisms of action of an antibiotic on
a bacterial cell. (LOC)
4. Explain a mechanism of antibiotic resistance. Provide an example.
(LOC)
5. Why aren’t antibiotics as effective in treating disease as they used
to be? (HOC)
Summative assessment:
1. The student will find and illustrate the mechanisms of
action of certain antibiotics and relate these actions of
antibiotics to steps in gene expression.
A2-A4
2. The student will be able to explain how resistance to
antibiotics arises from a change in the genetic material of
the cell.
A7
3. The student will be able to apply mechanisms of resistance
to antibiotics in bacteria to resistance to drugs in eukaryotic
cells.
A8
4. The student will propose strategies for the development of
new drugs.
HW
105
# of
bacteria
104
103
102
B
10
A
Time, hours
This graph shows a typical growth curve of a bacterium such as E. coli growing in liquid
culture.
1. What would the growth curve look like if antibiotic were added to the culture at the
beginning of the experiment (A)? Show at least two possibilities. What if you add two
antibiotics?
2. How would the curve change if you added antibiotic at the time designated by B?
Would the shape of the curve change for different antibiotics (cipro vs tetracycline) with
mechanisms of action that you learned about?