Mendel’s Peas and qs: Carla Cáceres, Renée Dawson, Tracey Hickox, Jonathan Marcot, Dick Mueller, Jon Seger, Thayne Sweeten Facilitators: Robin Wright, Lisa Lenertz Mendel in and out of the Garden Mendel’s Laws and some of their consequences

Set up  Prepare one envelope for each student in class with  4 blue paper clips representing homozygous dominant  2 blue and 2 green paper clips representing homozygous recessive  About 60% of the envelopes should be homozygous and 40% heterozygous to start with; in a 50 person class you’ll expect 1 or 2 (4%) of the offspring after the mating to be affected  Clickers will be useful for questions but not essential  Whiteboard or flip chart to record frequencies

Heredity Teachable Unit  The context  A large introductory biology course (>150 students)  Students are typically biology majors  Knowledge of students prior to this unit  Basic probability  Genes, alleles, chromosomes, chromatids, homologs, dominant and recessive

GoalsOutcomes students will be able to: 1. Understand and apply chromosome dynamics in meiosis to explain Mendel's law of segregation and independent assortment A. Draw chromosomes in gametes produced by heterozygous and homozygous parents B. Relate the products of meiosis to potential offspring of parents of known genotypes by using a Punnett square C. Calculate the probabilities of the various genotypes and phenotypes from well-defined crosses. 2. Extend Mendel’s principles from a pair of individuals to an entire natural population. A. Use a Punnett square to explain why the frequency of the recessive homozygote is q 2 in a randomly mating population. B. Generalize this principle to cases with multiple alleles (for example, the ABO blood-group locus). C. Given a clinically motivated case study, calculate probabilities of potential offspring genotypes and phenotypes.

Assessment  Formative assessments are woven throughout the teaching tidbit  think-pair-share exercises  iClicker polling  group discussion  Summative assessment  Bloom’s lower and higher order questions aimed at determining if the concepts can be transferred to other scenarios  Example: populations with different allele frequencies and applications to genetic counseling.

Assessment Question 1: In a population, where are the majority of recessive alleles for a lethal single-gene disorder found? Homozygous recessive Heterozygote Individuals who died because of the recessive disease Question 2: In a large population, 49% of individuals are BB, 42% are Bb, and 9% are bb. What percentage of the gametes produced will contain the little “b” allele? Lower Order Blooms Question 3: Explain why a deadly recessive disease persists in the population even though all people who are affected die before they reproduce. Higher Order Blooms

Diversity  1. Different types of formative assessment  Discussion (class and group)  What do you need to know  Predict risk of affected  Clicker questions  2. We did not use a real disease  Sensitivity to the risk among friends or family  Risks vary among populations  3. Unifying: we ALL carry potentially deadly mutations

The Teachable Tidbit Goal Provide concrete experiences that students can use to extend Mendelian laws from individuals to populations Give students a basis on which to build the subsequent graphs and simulations of population genetics

Huntington disease 1 in 25,000 Cystic fibrosis 1 in 2,000 Hemophilia 1 in 10,000 How many of YOU are carriers for these disorders? What is your risk? Phenylketonuria 1 in 12,000

Today we’ll examine the inheritance of a genetic disorder Green Paperclip Syndrome (GPS)

This disorder is determined by a single gene with two alleles: Blue and Green

In your envelope, you’ll find four paperclips. Think-Pair-Share: Why did we give you four? What does each paperclip represent?

Your GPS genotype Some of you may lack any green alleles. Some of you may be carriers. Some of you may be affected. Which allele is dominant? What terms do geneticists use for these allele combinations?

In a few minutes, you will combine your gametes (wink, wink) link the ol’ paperclips... to make offspring for the next generation.

2. For the entire class population, how many offspring in the next generation will be affected? 1. What are the chances YOUR offspring will be a carrier or affected? Think-Pair-Share: Do you need more information to answer these questions? If so, what information?

Clicker: Indicate your genotype A. Unaffected B. Carrier C. Affected

Prediction (via clicker) After mating, what percentage of offspring from the entire class do you think will have Green Paperclip Syndrome? A. Zero B.1-5% C.6-24% D.25% E.Greater than 25%

IMPORTANT Mating Instructions  Pair up with your neighbor.  Hold your envelope above your head  Without looking into your envelope, randomly choose a gamete  Link your two gametes together to represent your offspring

Clicker: ONE person in each mating pair should indicate whether your offspring is: A. Unaffected B. Carrier C. Affected

Earlier, we asked you to predict the percentage of offspring in the class population with Green Paperclip Syndrome. Does your prediction match the results?

Given that almost ½ of you had a recessive allele, why is the number of affected offspring so small? Given that almost ½ of you had a recessive allele, why is the number of affected offspring so small?

Bb B b BB (25%) Bb (25%) bb (25%) Bb (25%) p = 0.5 q = 0.5 p = 0.5 q = 0.5 BB (64%) Bb (16%) bb (4%) Bb (16%) p = 0.8q = 0.2 p = 0.8 q = 0.2

Bb p = 0.5 q = 0.5 p = 0.5 q = 0.5 B b BB (25%) Bb (25%) bb (25%) Bb (25%)

Bb p = 0.8 q = 0.2 p = 0.8 q = 0.2 B b BB (64%) Bb (16%) bb (4%) Bb (16%)

Things go crazy when Mendel escapes from the garden...

Where to next?  Try with different allele frequencies.  Try with mating limited to a table (island) and then repeat allowing an isthmus to form between some tables. Initial populations should have different allele frequencies. Gene pool  Pool all of the paper clips into a single collection.  Each person randomly picks a clip and links to the clip chosen by the following person.  See if prediction still works.

Other possibilities Link up paperclips into a chain, representing a chromosome. Use colored paperclips to represent genes/alleles. Can use to explore effects of linkage on inheritance Can use to explore effects of recombination on inheritance