Sun, Skin and Cancer

Author: Sarah Kenyon and Rachel Hughes

Time: 4 days
2.5 hrs

ABCD Overhead
Mole Overhead
Station 1- Layers of the Skin
Layers of the Skin Handout (enough copies for _ of the class staying at station)
Skin Jigsaw
Scientific illustrations of skin anatomy and/or biological models of the skin
Station 2 - Solar Ultraviolet Radiation impact on Yeast Cells
G948-1C Saccharomyces cerevisiae
Yeast-extract Adenine Dextrose Medium agar (available from Carolina Biological)
Enough Petri plates for 4 plates per student group (use plastic Petri dishes, Fisher if available)
Capped 13 x 100 mL culture tubes
Sterile water
1-mL pipettes
Glass spreader, paperclip spreader or Q-tips
Autoclave or pressure cooker
Diagram of UV spectrum
Station 3 - Where is Cancer from?
A couple of computer stations
Station 4- Skin Cancer
Student activity sheet for Skin Cancer
Skin diagram
Station 5- The Cell and Cancer
A couple of computer stations
Station 6- Tanning Taboo Article
Articles for each student from: http://www.kidshealth.org/teen/safety/safebasics/tanning.html


In this learning cycle, students will explore the importance of animal and human (clinical) trials. To do this, students will use the example of skin cancer and its relationship with UV exposure. The objective of this learning cycle is to develop an appreciation for the steps involved in biomedical research, as well as to arm students with information to help them best protect themselves and those they know from the effects of excessive UV radiation. To do this, students need to be introduced to basic skin physiology, so that they can develop reasoned questions over the course of the learning cycle. This lesson is a series of stations where the students explore skin anatomy, are introduced to the basics about cancer and explore the relationship between UV radiation and skin cancer. This lesson follows another lesson addressing clinical trials where students are provided with an article about skin cancer and clinical trials. This explore lesson allows students to answer questions prompted by the article and to develop their understanding of cancer and the skin so that they might explain their assigned article in the next lesson.

Students will:
1. Identify basic components of skin on a cross sectional diagram
2. Provide a basic description of cancer in terms of cell biology
3. Learn the ABCD of skin cancer/mole evaluation and perform their own evaluation of “test moles”
4. Name the three kinds of skin cancer and describe where in the skin they originate
5. Describe the impact of UV radiation on yeast cells and use this to suggest a relationship between sun and skin cancer.

National Science Standards
Content Standard A: Scientific Inquiry
Identify questions that guide scientific inquiry
Content Standard C: Life Sciences
The Cell
Content Standard F: Science in Personal and Social Perspectives
Natural and human-induced hazards

Teacher Background

UV Radiation and Yeast
When ultraviolet radiation hits living cells it is able to damage the DNA of the cells. Most cells have a mechanism to repair the mutations caused by ultraviolet radiation. Repeated damage increases the chance that a mutation will be missed by the repair mechanisms. In humans, this can cause skin cancer, wrinkles, and immune system damage.

The UV spectrum is divided into 3 parts: those that cause sunburns, UV-B; those with shorter wave lengths (UV-C) which don’t reach the earth; and UV-A which have longer wavelengths. Historically UV-B was considered the main culprit in skin damage. Recently, it has been recognized that UV-A, may be a more important factor in skin damage and specifically, the cause of skin cancers such as melanoma. Sunscreens were originally developed to protect from UV-B as UV-A appeared to have no immediate visible effect. Today, many sunscreens do attempt to block both UV-A and UV-B, but the SPF of a sunscreen is based upon its protection against UV-B not UV-A. In addition, many sunscreens are not very effective at blocking UV-A radiation. UV-B is implicated in basal cell carcinoma as it damages DNA in basal cells of the epidermis. The yeast cells being used at this station lack DNA repair enzymes, and so are killed by UV light.

Skin Cancer.

Resource Websites
ABCDs of skin cancer prevention exam;
This is a great basic web site about cell cycle and cancer. It includes a review of basic biology:



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 bag.

On Day 1:

  • Prepare a suspension of a known number of UV-sensitive yeast cells.
  • Sterilize 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
  • Using 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.

Day 1
1. As students enter the classroom, they should be directed to the overhead displaying a variety of different moles. Ask students to identify any that might appear suspicious to them. What characteristics do students use to identify whether or not the mole is one that should be seen 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 with their families.

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 unfamiliar with.

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 on the questions that will be supported by a better understanding of 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 trial described in their 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 the class will be working in groups at Station 1, the other half of class working in groups at Station 2. Tomorrow in the first part of class they will go to whichever station they didn’t attend today and then proceed with the other stations.

Days 2,3 and 4
1. Students should start by doing Station 1 or Station 2. Allow 30 minutes to do this.

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 to discuss and synthesis the main points from the stations. As a class identify the major ideas and list those on the board. Pay particular attention to connecting the information students gained about UV radiation and yeast to the other stations.

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

* Description
Print the description of the different layers of the skin. This has been taken from the following site: (http://dermatologychannel.net/skinanatomy/). Feel free to use another. This information is quite basic and could be found in a class textbook as well.

Station #1 -Layers of the Skin
Student Instructions

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

Station #2 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 also necessary.

Description: In this activity, students use UV sensitive yeast to investigate the effects of ultraviolet light from the sun on ultraviolet sensitive yeast cells.

Station #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. Given the various variables described above you are going to apply at least 3 different treatments to the yeast and monitor the damage.
You will grow the yeast on Petri dishes that have already been prepared.

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 treatment
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 contain 105 cells/mL. Remove 0.1 mL from this tube and place it by the tube containing 0.9 mL of distilled water. Mix. This tube will now contain 104 cells/mL. Continue this procedure until 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 thoroughly. You will have 10 mL of cells at 10^2 cells/ml. Aliquot 1 mL of this suspension into 6 epitubes.


v. Pour the entire contents of each epitube onto a separate Petri dish of Yeast-extract Adenine Dextrose medium.
vi. Spread the cell suspension across the plate to distribute the cells as evenly as possible by rocking and swirling the plate, or by spreading with a sterile 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 temperature.
x. Count the colonies on experimental and control plates.
xi. Calculate the surviving fraction by the following method:
Surviving fraction = irradiated colonies
colonies (control plate)

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 UV radiation under different treatments.

Station #3 What is a cancer from:
Provide: internet access, set computers up to the sites described above.
Description: Students review cell division and consider what might happen when cell division goes awry.

1. 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.

Station 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; (2000) 1:74
* 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 cancer)
* 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 developing the disease.
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.

Station 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 low.

Station #6 Tanning Taboo Article
Students read the article that can be found at: http://www.kidshealth.org/teen/safety/safebasics/tanning.html and/or http://www.fda.gov/cdrh/fdaandyou/issue07.html

Station 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. .


Embedded Assessment
6. Identify basic components of skin on a cross sectional diagram
7. Provide a basic description of cancer in terms of cell biology
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 skin cancer.


PULSE is a project of the Community Outreach and Education Program of the Southwest Environmental Health Sciences Center and is funded by:

NIH/NCRR award #16260-01A1
The Community Outreach and Education Program is part of the Southwest Environmental Health Sciences Center: an NIEHS Award


Supported by NIEHS grant # ES06694

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Last update: November 10, 2009
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