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: 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.

The Scaffold: In Previous Lectures… 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.

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

Simple Mendelian Traits Exercise - “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

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

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

Class Survey of a Continuous Trait: How Tall Are You? A5’ or shorter B5’1” – 5’4” C 5’5” – 5’8” D 5’9” – 6’ E 6’1” or taller Clicker data collection

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

Hypotheses for Normal Trait Variation Incomplete dominance Multiple genes Environment

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”

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

Mating Game: Debrief and Assumptions 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?

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 Trait Frequency Trait Frequency Trait Frequency

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

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

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