1. Mutagenesis and Cancer
Kamena Kostova and Darienne Myers

2. Overview of Darienne and Kamena’s Lessons
4 Lessons total on Cancer and Mutagenesis
1. Introduction to Cancer and Mutagenesis (yesterday)
2. Experiment Day! Testing Mutagenesis with Yeast (today, Friday 3/7)
3. Data Analysis (Monday, 3/10)
4. Group Presentations to discuss your experiments and results (end of next week)

3. Recap from Yesterday What is cancer? What tissues can get affected?
A disease; cells grow/proliferate like crazy (uncontrolled). This can lead to the formation of tumors
What tissues can get affected?
Any tissues
What are some causes of cancer?
Genetics, environmental factors (smoking, radiation, sun rays), personal habits (smoking, tanning), age, viruses
What is a mutation?
An alteration in a cell’s DNA that may change the expression and/or function of a protein

4. How do we study mutagenesis?
Model organisms!
We will use yeast (Saccharomyces cerevisiae)
Yeast are a good model system because:
They grow easily in the lab
Many genes are similar between yeast and humans
Lead the students to the idea of a model organism

5. Yeast: our model organism
Pictures of yeast
Single cells:
Growing on plates:
Growing in liquid:
Pictures of cheek cells
Explain that yeast can grow both in liquid and on plates. We’ll start with liquid yeast for our experiment, then will put it on plates to grow over the weekend. T

6. Mutagenesis Experiment
Today, you are going to do an experiment! You will test some of the substances you brought in to see if they can cause mutations in yeast
Why is this type of experiment important?
When new vitamins, drugs, chemicals, etc are developed, they need to be tested to determine if they are safe or if they may be cancer-causing (carcinogenic).
The test for this is based on an old experiment called the Ames Test, which was created in the 1970s and is still used today!

7. Yeast food
Yeast grow on plates (petri dishes) that contain nutrients. This is called “media.”
Scientists can choose what nutrients go into the media. They can also add different chemicals that might affect growth of the yeast. The chemical we will use today is called 5-FOA.
Yeast have genes that allow them to process some of these nutrients and chemicals. One of these genes is important for making uracil (URA).
5-fluoroorotic acid

8. Yeast food
5-FOA is a chemical that is toxic to yeast if the yeast have the URA gene.
If the yeast don’t have the URA gene, 5-FOA is NOT toxic.
Yeast
Plate with 5-FOA
Yeast
(have the URA gene)
Yeast DIE ☹

9. Yeast food
5-FOA is a chemical that is toxic to yeast if the yeast have the URA gene.
If the yeast have a mutation in the URA gene, 5-FOA is NOT toxic.
Yeast
(mutation in
the URA gene)
Plate with 5-FOA
Yeast GROW! ☺

10. Mutagenesis experiment
Today, we will start with yeast that HAVE the URA gene. Will they grow on 5-FOA plates?
NO. They will not grow.
Plate with 5-FOA
Yeast DIE ☹ Y
Plate with 5-FOA
Yeast GROW! ☺
Yeast
(have the
URA gene)
Yeast
(have a mutation
In the URA gene)

11. Mutagenesis experiment
What do you think will happen if we add mutagens to the yeast and grow on 5-FOA?
Plate with 5-FOA
Yeast DIE ☹ Y
Plate with 5-FOA
Yeast GROW! ☺
Yeast
(have the
URA gene)
Yeast
(have a mutation
In the URA gene)
Treat with
mutagens

12. Mutagenesis experiment
What do you think will happen if we add mutagens to the yeast and grow on 5-FOA?
Plate with 5-FOA
Yeast DIE ☹ Y
Plate with 5-FOA
Yeast GROW! ☺
Yeast
(have the
URA gene)
Yeast
(have a mutation
In the URA gene)
Treat with
mutagens
Some yeast
will get
mutations
in the URA gene
Do this interactively with the students. “Which yeast will grow on the normal plate?” “Which yeast will grow on the 5-FOA plate?”. Then can go through the cartoon answers on the next slide.
Plate with 5-FOA
Yeast with mutations
GROW
Yeast without mutations
DIE

13. Mutagenesis experiment
What do you think will happen if we add mutagens to the yeast and grow on 5-FOA?
Plate with 5-FOA
Yeast DIE ☹ Y
Plate with 5-FOA
Yeast GROW! ☺
Yeast
(have the
URA gene)
Yeast
(have a mutation
In the URA gene)
Treat with
mutagens
Some yeast
will get
mutations
in the URA gene
Do this interactively with the students. “Which yeast will grow on the normal plate?” “Which yeast will grow on the 5-FOA plate?”. Then can go through the cartoon answers on the next slide.
Yeast with mutations
GROW
Yeast without mutations
DIE
Plate with 5-FOA

14. Mutagenesis experiment
What do you think will happen if we add something that is NOT a mutagen to the yeast and grow on 5- FOA?
Plate with 5-FOA
Yeast DIE ☹ Y
Plate with 5-FOA
Yeast GROW! ☺
Yeast
(have the
URA gene)
Yeast
(have a mutation
In the URA gene)
Treat with a non-mutagen
Yeast will still have the URA gene
Reinforce that the yeast we are working with aren’t actually blue and green ;)
Plate with 5-FOA
Yeast without mutations
DIE

15. Let’s do an experiment!
We will give each group some yeast (NO mutation in the URA gene) and a 5-FOA plate
Pick a substance (potential mutagen) to test (you can bring it from home or choose something we brought)
Some of the yeast will be left untreated, this is your control
Some other yeast will be treated with your potential mutagen (mut X)
Make a prediction:
Will the control yeast grow on the 5-FOA plate?
If your substance is a mutagen, do you expect to see colonies on the plate?
If your substance is not a mutagen, do you expect to see colonies on the plate?

16. Examples of mutagenesis plates
EtBr
coffee
pepper
Soy Sauce PB
Coke
Control
Lysol
Sriracha
vinegar
Salt
tea