Download Phenotype of Breast Cancer (PowerPoint) Northwest 2011

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Participants:
Facilitator:
Virginia Carson
Chris Tubbs
Charlie Janson
Devon Quick
John Reiss
Melissa Rowland-Goldsmith
Mark Wilson
Students will understand characteristics of
evidence in science

Students will confidently choose and defend
evidence-based positions

Students will understand the relationship
between genotype and phenotype


Students have covered concepts of
 Probability vs. frequency
 Mutations
 Genotype
 Phenotype
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Students will be able to interpret a graph
relating genotype to phenotype

Students will be able to recognize and
interpret environmental effects on
phenotype/genotype relationships

Students will be able to apply the
concepts of expressivity and penetrance
to an example of population variation
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Background:


Normal BRCA is protective gene against breast cancer
(codes for a tumor suppressing protein)
Some people have BRCA gene mutation that makes the
protective protein non-functional (tumors not suppressed)
 Several mutations of this gene identified
A. Yes
B. No
GROUP A
genotype A1/A1:

The frogs in population A are genetically
identical and look the same.
GROUP A
genotype A1/A1:
GROUP B
genotype A2/A2:


The frogs in B are also genetically identical (to
each other)
What might explain why some B frogs have
spots and other do not? (shout out)
GROUP A
genotype A1/A1:
GROUP B
genotype A2/A2:
GROUP C
Genotype A3/A3:


The frogs in C are genetically identical (to each
other), but have variable numbers of spots
What is different about the pattern of variation
in C compared to B? (talk with your neighbor)
http://www.herpnet.net/IowaHerpetology/index.php?option=com_content&task=view&id=29&Itemid=26
GROUP A
genotype A1/A1:
Complete penetrance
GROUP B
genotype A2/A2:
Incomplete penetrance
GROUP C
Genotype A3/A3:
1 – minute paper,
then swap
Complete penetrance,
variable expressivity
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
Genotype is NOT always =
Phenotype!
Environmental factors and chance
events affect both penetrance and
expressivity
A. Yes
B. No
What does this red line tell you?
(shout out)
A. Yes
B. No


You could do some research on this and list
specific environmental effects, chance and
genetics as making someone more susceptible
to developing breast cancer, but simply having
the gene mutation on BRCA does not mean one
will always develop breast cancer.
The severity of breast cancer relates to
expressivity. If one breast is affected or two or
the ovaries as well – the more cancer, the more
expressivity.
A. Yes
B. No
C. Sometimes?

Q: which of these is
true?
A.
Most people with breast
cancer have the BRCA1
mutation
B. BRCA1 mutation is
100% penetrant
C. More than 50% of
people with BRCA1
mutation will develop
breast cancer

You should be more familiar with
graphical representation of data

You should recognize that environment
and genotype influence phenotype

You should be able to define and apply
the concepts of expressivity and
penetrance to an example of population
variation

Your sister has just met with a genetic counselor.
The genetic counselor told her that she had the
mutated form of the BRCA1 gene and provided her
the accompanying graph.
1. Explain to your sister why this is not a death
sentence.
2. How is this example relevant to the idea that
genotype does not equal phenotype? Hint: use
the words penetrance and expressivity.