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Group 7. Heritability

Group 7. Heritability. “The Nads” Jane Caldwell Jonathan Cumming Michelle Momany Rob Reenan Katrina Stewart Kathrin Stanger-Hall Kathy Takayama. The Teachable Unit: Genetic Basis of Continuous Traits. Learning Goals and Intended Outcomes:

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Group 7. Heritability

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  1. Group 7. Heritability “The Nads” Jane Caldwell Jonathan Cumming Michelle Momany Rob Reenan Katrina Stewart Kathrin Stanger-Hall Kathy Takayama

  2. The Teachable Unit:Genetic Basis of Continuous Traits Learning Goals and Intended Outcomes: • Compare and contrast patterns of inheritance for traits exhibiting dominant-recessive and incomplete dominance behaviors. • Given a frequency distribution of traits in a population, predict the genotypes, and vice versa. • Explain the genetic basis for the normal distribution of a trait in a population.

  3. Previous Lecture: Students will have mastered the basics of genes Chromosomes, DNA Gene replication Students will have been exposed to the concepts of heredity Simple Mendelian inheritance Dominant-recessive behavior Previous Homework: Develop an analogy or representation to explain simple inheritance. Include the terms below: Gene, dominant & recessive alleles, genotype, phenotype Groups shared this with another group at the beginning of the current lecture for engagement. The Scaffold:In Previous Lectures…

  4. Revisit: Mendel’s Peas • Certain traits exhibited specific patterns described by dominant/recessive behavior • Two phenotypes • Set population ratios • Such behavior is also evident in humans

  5. Simple Mendelian TraitsExercise - “Pair-Ear-Share” • Based on the distribution of traits in a population, scientists can make inferences about the genetics of inheritance in humans • Pair-Ear-Share • My ear lobe is: • A-Detached • B-Attached Detached Attached Clicker data collection

  6. Single Gene Incomplete Dominance • Systems often exhibit discrete yet complex phenotypic patterns • Four O’Clocks • Flowers have simple patterns of inheritance • No clear dominance • Incomplete dominance http://library.thinkquest.org/20465/genes.html

  7. Population Variation - Continuous Traits • Phenotype frequency patterns often do not match those we have investigated, e.g., pea seed shape, earlobe attachment • Continuous variation in trait - cholesterol • Normal distribution in frequency

  8. Class Survey of a Continuous Trait: How Tall Are You? • A 5’ or shorter • B 5’1” – 5’4” • C 5’5” – 5’8” • D 5’9” – 6’ • E 6’1” or taller Clicker data collection

  9. Hypotheses for Continuous VariationGroup Discussion and Hypothesis Development • Group discussion - 2 minutes • Generate a hypothesis to explain this height distribution

  10. Hypotheses for Normal Trait Variation • Incomplete dominance • Multiple genes • Environment

  11. The Mating Game:Multiple Gene-Incomplete Dominance Activity • Using coins and a cup, we will generate distributions of “coinotypes” that will be analogous to genotypes in a population • The penny is one gene • Alleles P (heads) and p (tails) • The nickel is another gene • Alleles N (heads) and n (tails) • These two “genes” control the same trait • Tossing a penny and a nickel together will generate the genotype of your gamete • Score your tosses with your “mate”

  12. The Mating Game:Multiple Gene Incomplete Dominance Activity • Roll twice, each “parent” record one offspring genotype • Scoring the genotypes of your offspring: A = 0 heads B = 1 head C = 2 heads D = 3 heads E = 4 heads Clicker data collection

  13. Does the curve approach normality? How many categories? If you had another contributing gene, how would the categories change? What constraints has the analogous system of coins placed on our genotypes? Mating Game:Debrief and Assumptions

  14. Frequency Trait Frequency Trait Frequency Trait Traits and Distributions Summary • Single gene, dominance • Discrete phenotypes • Discrete distributions • Single gene, incomplete dominance • Discrete phenotypes • Discrete distributions • Multiple genes, incomplete dominance • Continuous phenotypic traits • Continuous (normal) distributions

  15. Why Should We Care? • Most human traits are multigenic • For diseases, treatments are not simple • Multiple genes • Multiple targets for treatment • For next week, organize your group and identify a human disease that involves multiple genes • Google: polygenic disease • Select one and develop a 2 minute presentation for another class group

  16. Unit: Genetic Basis of Continuous Traits • Scaffold (previous activities): • Active learning assignment • Lectures Basic concepts of heredity Review of background: Active learning exercise: “Pair-Ear-Share” Single gene incomplete dominance example transition • Continuous traits: • Active learning exercise: Height • Students generate hypothesis Representation of traits in a population & Genetic basis of normal distribution • Mating game: • Active learning exercise: Coins • Generation of data • Analysis of data • Extension to more complex situations

  17. Thanks to Lianna & the Summer Institute GO-NADS!!

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