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Heredity Tidbit

Heredity Tidbit. Participants: Facilitator: Virginia Carson Chris Tubbs Charlie Janson Devon Quick John Reiss Melissa Rowland-Goldsmith Mark Wilson . Learning goals. Students will understand characteristics of evidence in science

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Heredity Tidbit

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  1. Heredity Tidbit • Participants: Facilitator: Virginia Carson Chris Tubbs Charlie Janson Devon Quick John Reiss Melissa Rowland-Goldsmith Mark Wilson

  2. Learning goals • 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

  3. Context • Students have covered concepts of • Probability vs. frequency • Mutations • Genotype • Phenotype

  4. Learning outcomes • 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

  5. The phenotype of breast cancer • 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

  6. Clicker Question:Do genes cause breast cancer? • Yes • No

  7. Look at my Frogs GROUP A genotype A1/A1: • The frogs in population A are genetically identical and look the same.

  8. Look, more Frogs 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)

  9. Oh wait, I have more Frogs 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)

  10. What caused all the variations? http://www.herpnet.net/Iowa-Herpetology/index.php?option=com_content&task=view&id=29&Itemid=26

  11. Scientific jargon GROUP A genotype A1/A1: GROUP B genotype A2/A2: GROUP C Genotype A3/A3: Complete penetrance Incomplete penetrance Complete penetrance, variable expressivity 1 – minute paper, then swap

  12. Summary • Genotype is NOT always = Phenotype! • Environmental factors and chance events affect both penetrance and expressivity

  13. Clicker Question:So, now what do you think, does a gene cause breast cancer? • Yes • No

  14. Incidence of breast cancer vs. age of women in US

  15. Incidence of breast cancer vs. age of women in US

  16. Incidence of breast cancer vs. age of women in US What does this red line tell you? (shout out)

  17. Clicker Question: Using the graph, will everyone with the BRCA mutation develop breast cancer? • Yes • No

  18. Factors associated with Breast Cancer • 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.

  19. Clicker Question:What do you think now? Does a gene cause breast cancer? • Yes • No • Sometimes?

  20. Breast Cancer Incidence • Q: which of these is true? • 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

  21. Putting it in a Bigger Context:Breast cancer and BRCA1 incidence in US women

  22. After today • 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

  23. Summative assessment: Essay Question • 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. • Explain to your sister why this is not a death sentence. • How is this example relevant to the idea that genotype does not equal phenotype? Hint: use the words penetrance and expressivity.

  24. Alternative graph that could be used, includes family history

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