Teacher Preparation Prior to class
A couple of days before the class prepare the Yeast-extract
Adenine Dextrose Medium agar plates. You will need enough
for 4 plates per group. Cover the flask and sterilize
for 10 minutes at 15 psi in an autoclave or pressure
cooker. Allow it to cool until you can touch it and pour
plates. When the agar has solidified, invert the plates
and store them at room temperature in a closed plastic
- Prepare a suspension of a known number
of UV-sensitive yeast cells.
tubes of distilled water for use in serial dilution.
Use 13 X 100mm tube with caps.
- (2 mL of dH2O in one tube,1 mL of dH2O in 6-8 tubes, 0.9
mL of dH2O in 10 tubes)
- Sterilize pipettes
a sterile toothpick, or a bacteria transfer loop, place
a small amount of yeast cells (about the size
of a head on a pin) from your source into the tube
containing 2 mL of
distilled water. Mix thoroughly. Perform a
serial dilution using the tubes that have 1mL of distilled
water in until
you use all your tubes (1 mL from tube1 to
tube 2; 1 mL from tube 2 to tube 3, etc.) Remember
to mix all tubes thoroughly
between dilutions to suspend the cells evenly.
Select the last suspension that is just barely cloudy
to the naked
eye. This last suspension will contain between 1 and 2 million
cells/mL. We will assume 106 cells/mL
- Repeat this procedure by the number of groups who will be
doing Station #2 on Day 1 to provide them each with a tube
of yeast in suspension.
On Day 2:
- Repeat the preparation of the suspension of UV-sensitive
yeast cells for the remaining groups.
1. As students enter the classroom, they should be
directed to the overhead displaying a variety of
Ask students to identify any that might appear
suspicious to them. What characteristics do students
identify whether or not the mole is one that should
by a doctor?
2. Once students have discussed the example moles,
share with them the ABCDs of skin examination
and review the
example moles; are they able to identify suspicious
moles? http://www.aad.org/public/Parentskids/KidsConnection/KCcancerABCDs.htm Encourage students to perform this examination
of moles on themselves and to share this information
3. As a class, brainstorm what they know about
skin cancer and how it develops.
Identify any questions that they
have, any areas that, as a class, they are
4. At this point remind students of their homework,
students were to review the article and
to come up with three
questions. Start class by asking what questions
they have about their articles. Focus students
questions that will be supported by a better
skin anatomy, cancer and the relationship
between UV radiation
and skin cancer.
5. Explain to students that they are going
to have to present and explain the clinical
article. So that they might be able to
do this well, they’re going to spend the
next few days exploring skin anatomy, cancer
and the relationship with UV radiation.
6. Briefly describe each of the stations
to the students. Explain that today half
in groups at Station 1, the other half
of class working in groups at Station
the first part
of class they will go to whichever station
attend today and then proceed with the other
Days 2,3 and 4
1. Students should start by doing Station
1 or Station 2. Allow 30 minutes to
2. Students should then proceed to
the other stations at their own pace.
3. When students are finished with
all the stations gather as a group
main points from
the stations. As a class identify
the major ideas and list those
on the board.
connecting the information students
gained about UV radiation and yeast
to the other
Station #1: Layers of the Skin
Provide students with:
Pictures or biological models of the dermis and epidermis:
Dermis and epidermis: http://www.biorap.org/tg/tgsun1skindetail.html
Epidermal layers: http://distance.stcc.edu/AandP/AP/imagesAP1/skin/skin.jpg
Print the description of the different layers of the skin. This has
been taken from the following site: (http://dermatologychannel.net/skinanatomy/).
free to use another. This information is quite basic
and could be found in a class
textbook as well.
#1 -Layers of the Skin
Time: _ hour
1. Individually, use the information provided to answer the
following questions in your notebook.
i. Describe the progress of a keratinocyte throughout its life
in the epidermis.
ii. What are the functions of the dermis and the epidermis?
iii. Where are melanocytes found?
iv. What skin structure is responsible for your fingerprints?
2. Individually, solve the jigsaw and label it. This should
be attached to your notebook.
3. As a group discuss how you might make a model of the skin
using household materials. Come up with a plan to create this
model. You will have to present it as a group at the end of
four days. The model will be assessed based on completeness,
matters of scale, and reflection of function
UV Radiation and Yeast –
Based upon lessons from ; http://www.phys.ksu.edu/gene/d1.html and Ray Day from Access Excellence: http://www.accessexcellence.org/LC/OP/RAY/
Provide enough culture tubes, sterile water, pipettes, tubes
with yeast suspension, cotton swab applicators, and Yeast-extract Adenine
Dextrose media plates for each group. A diagram of the UV spectrum is
Description: In this activity, students use UV sensitive
yeast to investigate the effects of ultraviolet light
from the sun on ultraviolet sensitive yeast cells.
#2 Solar Ultraviolet Radiation impact on Yeast Cells
Ultraviolet photons from the sun are potentially very dangerous.
The upper atmosphere, the stratosphere, filters most of this
radiation out, but enough can reach the earth that, depending
on where you are located, it can damage your skin and eyes
if you are exposed for too long. The amount of time you can
safely be exposed depends upon several variables:
1. Time of day
2. Cloud cover/haze
3. Altitude (typically means less haze)
4. Amount of direct exposure to UV (Are you in the shade? Are
you wearing clothes that can protect you from direct exposure?)
5. Use of sunscreen
6. Use of glass and most plastics as they can absorb some UV
7. How much of the skin pigment melanin you have. Melanin absorbs
UV and protects the skin.
You are going to use a UV sensitive strain of yeast that
is unable to repair its DNA when damaged by UV radiation.
the various variables described above you are going to apply
at least 3 different treatments to the yeast and monitor
You will grow the yeast on Petri dishes that have already
i. You will need 6 Petri plates per group.
ii. As a group, decide upon the treatments you are going
to apply to each plate. For each treatment suggest a control
iii. Obtain a tube with yeast suspension from your teacher.
This culture tube has a suspension that will contain between
1 and 2 million cells/mL. We will assume 106 cells/mL
iv. Using this tube set up a series of dilutions to reach
102cells/mL. You will need 1 mL of 102cells/mL for each
plate. Be sure that
the cells for each experimental/control pair is from the
same dilution batch:
Dilution Remove 0.1 mL of the suspension that you received
from your teacher and place it in the tube containing 0.9
mL of distilled water. Mix thoroughly. This tube will now
105 cells/mL. Remove 0.1 mL from this tube and place it
by the tube containing 0.9 mL of distilled water.
tube will now contain 104 cells/mL. Continue this procedure
you have 4 tubes. The fourth tube should contain 103 cells/mL.
Mark each tube with the number of cells/mL. Add 9 mL of
water to the 1 mL in the 103cells/mL tube and mix
will have 10 mL of cells at 10^2 cells/ml. Aliquot 1 mL
of this suspension into 6 epitubes.
DO NOT SPREAD THE CELLS UNTIL YOU ARE JUST READY
TO DO THE EXPERIMENT
v. Pour the entire contents of each epitube onto
a separate Petri dish of Yeast-extract Adenine
vi. Spread the cell suspension across the plate to
distribute the cells as evenly as possible by rocking
the plate, or by spreading with
q-tip (use a new q-tip for each plate). (An alternate and probably more
accurate method is to pipette 0.1 mL from each of the
tubes and use a bacteria spreader
to spread this reduced amount of material.)
vii. Allow 15 minutes to a half-hour for the yeast suspension to be absorbed
by the agar. Keep plates in the dark during transportation.
viii. Expose the plates to sunlight or the particular treatment you have
assigned for exactly 3 1/2 minutes. LEAVE THE LIDS ON THE PETRI DISHES!
The UV light
will pass through the plastic.
ix. Incubate the exposed and the control plates until the colonies are
large enough to count. This should be 2 days at 30 degrees C and 3-4
days at room
x. Count the colonies on experimental and control plates.
xi. Calculate the surviving fraction by the following method:
Surviving fraction = irradiated colonies
xii. Make sure to note when you expose the yeast,
what date, what time and the conditions.
xiii. Tabulate your data with the rest of the class. What patterns
do you notice? Write your results drawing conclusions about the about
What is a cancer from:
Provide: internet access, set computers up to the sites described
Description: Students review cell division and consider what
might happen when cell division goes awry.
Drawing upon your biology background, explain how cell
division helps an organism stay alive and healthy.
2. What would happen if mitosis within an organism were uncontrolled?
3. What do you think regulates cell division in organisms?
Watch the video How Cancer Cells Grow and Divide QuickTime
Video and animation 1 at the Cell Biology and Cancer NIH supplement
site. Discuss the following:
4. Describe in your own words what a cancer cell is. Come up
with an analogy to describe it.
5. What other kinds of signals do you think cells would respond
to that would make them grow and divide appropriately?
6. Why do you think the oncogene acts as though it is stuck
in the "on" position?
7. How might scientists use knowledge about receptors and also,
how metastasis occurs to find ways to stop cancer?
Discuss the following:
1. What are some ways cancer cells develop abnormally?
2. What are some ways that cancer cells differ from normal
cells of the same kind of tissue?
3. How does the body respond to cancer cells?
Station #4: Skin cancer
Provide: articles downloaded about different types of skin
cancer. The Merck website http://www.merck.com/mmhe/sec18/ch216/ch216a.html has good information sheets on basal cell, squamous cell and melanoma
cancers. Using the diagram provided and the information provided on
the Merck site, students should identify where different cancers appear
in the skin layers.
Description: At this station students review the 3 types
of skin cancer.
4- Skin Cancer
At this station you need to use the information provided to
identify on the diagram where different types of skin cancer
originate. After reading the information identify your own
risk factors for skin cancer and describe methods you currently
use to protect your skin and any that you might adopt now.
Melanoma: Melanoma is in epidemic growth at ~ 3% rise in cases
per year in the USA
* 53,000+ new cases reported yearly / 7800+ deaths yearly
* Melanoma risk: (1935) 1:1500; (1960) 1:600; (1985) 1:150;
* Fastest growing cancer currently in the USA and worldwide
* Most common cancer in young adults aged 20-30
* Currently MORE new cases of melanoma occur than do HIV/AIDS
* Women age 25-30: melanoma = primary cause of cancer death
* Women age 30-35: melanoma = #2 cause of death (after breast
* Many Americans are particularly at risk for skin cancer because
of our outdoor lifestyle and desire to look tanned and healthy.
* Sunburn is not the only cause of skin cancer. Tanning or
just too much sun, year after year, can also lead to people
Our high rate of skin cancer and melanoma in particular, is
disturbing, especially given that most melanoma is preventable
if detected at an early and treatable stage.
Station 5 – The
Cell and Cancer
Provide: Internet access
Description: Students use an online website as a review of
biology basics so that they can understand the nature of cancer.
5- The Cell and Cancer
You are going to use a set of online materials to review basic
biology and be introduced to cancer biology. Read each page
and answer the questions at the end of each page. Most of this
material should be a review. Please make sure to answer the
following questions in your notebook:
1. Explain why cancer cells keep growing even though the original
mutation happened in only a single cell.
2. Breast, testicular and skin cancers have good survival rates.
Suggest why this may be the case.
3. 40 cases out of 100 are not diagnosed until the cancer is
advanced or needs extra treatment after surgery. Out of this
group of people, how many are cured?
Suggest a reason why the number cured from this group is so
Station #6 Tanning Taboo Article
Students read the article that can be found at: http://www.kidshealth.org/teen/safety/safebasics/tanning.html
6 –Tanning Taboo
Using the information provided in the article, draw a flow
diagram in your notebook to show what happens when the skin
receives too much UV radiation. .
Identify basic components of skin on a cross sectional
7. Provide a basic description of cancer in terms of
8. Name the three kinds of skin cancer and describe where
in the skin they originate
9. Describe the impact of UV radiation on yeast cells
and use this to suggest a relationship between sun and