UV Protection Power
How well does your product
protect you from skin cancer?
What do you know
about
1. What is UV Light?
2. Why is UV Light
Dangerous?
What claims about sun protectants have
you heard during your lifetime?
From whom or where did you hear such
claims?
How do scientists evaluate such claims?
Product Investigation
Read your advertisement
In your notebook
• Identify the explicit (obvious) claims about
UV light and cancer
• Identify the implicit (implied) claims about
UV and cancer
• What evidence is offered to support the
claims?
As a Group
Prepare a white board presentation:
What is your product?
What claims does it make?
What evidence supports the
claims?
Do the claims seem reasonable?
Sun Radiation
Visible light – what we see
Wave length 380 nm to 760 nm
Invisible Light
What we cannot see
Infrared: greater than 760
Long waves – low energy
Feels warm
Ultraviolet: shorter than 380
Short waves - High energy
Can cause sun burn and eye damage
Cellular Effects of
Ultraviolet
High energy waves interact with DNA
Can cause mutations
Mutations can lead to skin cancer
depending repeat exposure, age,
genetic factors
Can burn fovea leading to blindness
The Multi-step Process of
Cancer
Initial mutation
Normal cell
Pre-cancerous cell
Slow Clonal Expansion
Metastisis
Additional mutations
Rapid Growth
Cells fight back
To be able to survive in a world with
sunlight, early cells developed ways to
repair DNA
Four different mechanisms have been
identified
Our cells use the exact same mechanisms
to repair sun damage as bacteria and yeast
Repair must occur before DNA replication
and cell division
In this experiment
We will use haploid yeast cells that
reproduce asexually (cloning)
Wild strain yeast has 4 known repair
mechanisms (like most humans)
Mutant yeast lacks 3 of the repair
mechanisms
DNA Repair
How do skin cells protect
their DNA from UV light
so there’s no need for
repair?
How do eye cells also protect
their DNA from UV Light?
Iris
Eye Damage From UV Light
Cataracts – cloudy lens
Retinal damage (macular
degeneration)
Snow blindness – burned cornea
Eye cancer (18 different kinds)
www.eyecancer.com
• What are yeast?
• Why are yeast good
organisms for testing
claims about UV light?
Picture by Carsten Kettner
X
The UV sensitive yeast dies
from the mutations.
The more UV light, the more
yeast cells die, the fewer the
colonies on the petri plate
Lots of UV light
No UV light
Can your product protect the UV
sensitive yeast from the deadly
UV light?
Make your hypothesis
Research
Find three
specific facts
from the
notes for
background
information.
Write Hypothesis
Using the research and your
general knowledge, write a
hypothesis on your paper as to
how well your product will
protect the yeast from the
UV light.
Experimental materials
UV sensitive yeast
Petri plates with YED
agar
Product you are
testing
Piptettes and swabs
Sterile water
Designing your experiment
Make sure you have controls.
Decide how you will simulate your product
to protect your yeast from the sun.
Use the shoe boxes to carry your prepared
plates to and from the sun
Put your plates wrapped in aluminum foil
and labeled into the incubator when
finished.
Prepare dilution by adding one
small colony of yeast to water.
Swirl the tube to distrubute evenly.
Set up Experiment
1 ml
Follow directions to
inoculate your petri
dishes.
Stock plate
10ml of
Sterile water