Download Hardy-Weinberg Lesson Plan 4

Raja Ali
Patrick Cole
Scott Housel
Page 1 of 8
EDU T&L 750
August 2, 2010
Hardy-Weinberg Equilibrium Lesson Plan
Grade 9-12
Applicable Ohio Academic Content Standards:
Life Sciences
Benchmarks (9 – 10)
C. Explain the genetic mechanisms and molecular basis of inheritance.
E. Explain how evolutionary relationships contribute to an understanding of the unity and
diversity of life.
H. Describe a foundation of biological evolution as the change in gene frequency of a
population over time. Explain the historical and current scientific developments,
mechanisms and processes of biological evolution.
Benchmarks (11 – 12)
C. Explain how the molecular basis of life and the principles of genetics determine
inheritance.
Mathematics
Benchmarks (8 – 10)
Patterns, Functions and Algebra Standard
G. Solve quadratic equations with real roots by graphing, formula and factoring.
Benchmarks (11 – 12)
A. Analyze functions by investigating rates of change, intercepts, zeros, asymptotes, and
local and global behavior.
B. Use the quadratic formula to solve quadratic equations that have complex roots.
Technology
Benchmarks (11 – 12
F. Classify, demonstrate, examine and appraise medical technologies.
Technology Use Overview
In this lesson we will be using Turning Point technology, a Smart Board presentation, and
website teaching resources/virtual manipulatives. The Turning Point technology will allow
us to give a diagnostic assessment at the beginning as well as a summative assessment at
the end of our lesson. We will use the Smart Board to present our lesson in a way that
allows us to interact with, manipulate, and add to the presentation as it is given. The
website resource will be used to present the math aspects of the lesson and allow for
formative assessment.
Raja Ali
Patrick Cole
Scott Housel
Page 2 of 8
EDU T&L 750
August 2, 2010
Hardy-Weinberg Equilibrium Lesson Plan
Grade 9-12
Student Objectives
After completion of this lesson, the student will be able to:
 Explain how changes in allele frequency result in evolution.
 Explain what the Hardy-Weinberg equilibrium equation is used for. Explain the
significance of the equation. Recognize the equation’s mathematical properties.
 Explain how dominant and recessive alleles can change frequency in a population.
 Describe practical applications of the Hardy-Weinberg equation (i.e. determining
frequency of individuals carrying alleles for diseases such as cystic fibrosis).
 Calculate genotypic and allelic frequencies for given, hypothetical populations.
 Discuss conditions under which a population is in Hardy-Weinberg equilibrium.
Accommodations for different learning styles and levels will be made by presenting the
information in multiple ways (i.e. spoken, written, visual, interactive) and through
formative and summative assessment that challenge different levels of learners.
Purpose/Rationale for Lesson
The Hardy-Weinberg equilibrium equation is an important component in the study of
population genetics. Population genetics is measured by allele frequency and genotype
frequency. A change in allele frequency over time is defined as evolution. In order to
determine if evolution is occurring in a population, scientists first need to know what to
expect if evolution is NOT occurring. By comparing hypothetical, predicted allele/genotype
frequencies with what is actually observed in a population, scientists can determine if
evolution is occurring.
Hardy-Weinberg equilibrium defines a situation in which evolution is NOT occurring. This
model operates under the following assumptions:
1.
2.
3.
4.
5.
Very large population size.
Isolation from other populations.
No net mutations.
Random mating.
No natural selection.
Students will have prior knowledge of alleles, genes and gene pool. As well as be familiar
with quadratic functions and their properties.
Opening/”Hook”
Students will be “hooked” into the lesson by the following engaging questions:
Raja Ali
Patrick Cole
Scott Housel
Page 3 of 8
EDU T&L 750
August 2, 2010
Hardy-Weinberg Equilibrium Lesson Plan
Grade 9-12
Why don't dominant alleles dominate in a population?
Why aren't recessive traits gradually "swamped out," so they disappear from the
population?
 How can we estimate the probability of inheriting genetic diseases?


These questions are followed by a cheesy introduction to the lesson from none other than
Mr. Godfrey Hardy and Mr. Wilhelm Weinberg themselves. Students will hopefully find this
mildly amusing.
Finally, the students will be engaged in a brief diagnostic assessment via Turning Point
clicker questions. The subject for these questions will be information covered in a previous
introductory lesson on genetics. Prior knowledge of these introductory concepts is
necessary to understand today’s lesson on Hardy-Weinberg.
Lesson (estimate 50 minute class period)
Intro/Science Lesson (estimated at 15 minutes):
1. Raja, Scott and Patrick introduce themselves to the class.
2. Patrick engages class with “thought-provoking questions.” This is intended as an
informal diagnostic assessment to gauge the class’ existing understanding of
genetics.
3. Continue to introduce today’s topic through SmartBoard slides. Describe history of
Hardy and Weinberg. Hardy was a mathematician in England, was friends with
Punnet (of the Square fame) and regularly played cricket with him. Punnet inspired
him to consider the subject of genetics. Weinberg was a physician in Germany. He
specialized in delivering babies, and consequently spent a lot of his time researching
inheritance, specifically in twins. Both published their papers the same year, but
Weinberg wasn’t given credit for 35 years, since his was published in German and
most people didn’t read it.
4. After introduction, engage class in a review of basic genetic concepts covered in
prior lessons. Questions will be in TurningPoint multiple-choice format and
students will respond with clickers. This also functions as a diagnostic assessment
for students. Questions to be asked include:


What is an allele? One of two or more forms a gene can take
What does genotype mean? The genetic makeup of an organism
Raja Ali
Patrick Cole
Scott Housel
Page 4 of 8
EDU T&L 750
August 2, 2010
Hardy-Weinberg Equilibrium Lesson Plan
Grade 9-12




What does heterozygous mean? Having two alleles that are different
What does homozygous mean? Having two of the same allele
What is a population? A localized group of interbreeding individuals of the same
species
What is evolution? Change in allele frequencies in a population over time
5. Following the review, introduce the following concepts of “Population Genetics”





Evolution occurs at the population level. Individuals don’t evolve. Populations
of species do, and it occurs over a lengthy period of time.
All the interbreeding individuals in a population share a common group of genes
called the gene pool.
Each gene pool contains all the alleles for all the traits of the population.
For evolution to occur in the population, some of the genetic frequencies must
change with time.
Allele frequency means the number of times an allele for a particular trait occurs
compared to the total number of alleles for that trait.
Allele Frequency 
number of specific type of allele
the total number of alleles in the gene pool
6. Continue discussion of evolution. Reiterate what evolution is, and describe the five
mechanisms of evolution:





Mutation – a permanent, heritable change in the DNA of one or more
chromosomes. Usually a base-pair substitution.
Migration – genes are exchanged between different populations. Give examples
of individuals leaving one population and joining another, bringing new genes.
Non-random mating – certain organisms with specific genotypes are preferred
in the population, mate more often, and have more offspring to pass their alleles
to. Give examples of mating displays. Alpha-male gorillas, peacock tail-feather
displays, etc.
Genetic drift – random, chance events change allele frequencies in a population.
Give examples of catastrophic events wiping out most of a population.
Natural selection – organisms with certain traits are better suited to survive in
an environment and will survive to pass the alleles for the beneficial traits to
their offspring.
7. Explain the Hardy-Weinberg law. It is a model of a population that DOES NOT
evolve. Used for comparison to real populations that DO evolve. Hardy-Weinberg
Raja Ali
Patrick Cole
Scott Housel
Page 5 of 8
EDU T&L 750
August 2, 2010
Hardy-Weinberg Equilibrium Lesson Plan
Grade 9-12
equilibrium removes all mechanisms of evolution. The following conditions must be
met for a population to be in Hardy-Weinberg equilibrium:





Random mating – There is no mating preference in the population. All
organisms have an equal shot
No migration – There is no gene flow in or out of the population. No-one
enters or leaves the population
Large population – The population never decreases drastically. No big
changes, like in genetic drift.
No mutation – No random changes in DNA produce no new alleles.
No natural selection – All organisms in the population are equally fit.
If any of these conditions are violated, allele frequencies will change in the
population, and if allele frequencies change, evolution occurs.
8. At this point, Raja takes over the lesson to cover the mathematical aspects of the
Hardy-Weinberg equilibrium equation.
Math Section of Lesson (estimated 15 minutes)
1. Once the idea behind evolution and its requirements have been discussed, we’ll
begin introducing the equation. We’ll start with labeling the frequency of dominant
and recessive alleles as p and q accordingly. We then note that the sum of p and q
equals the sum of frequencies of both alleles, which equals 1.0 ( decimal form of
100%). Then we’ll have the class square both sides (see below). This will result in a
quadratic.
2. The class would be familiar with quadratics and how to solve them. We’d take a few
minutes to discuss/review the various forms of the quadratic with the class; then
we’ll explain that for the purposes of the Hardy-Weinberg equation, we’ll want the
quadratic in general form. Then we’ll discuss what the new terms represent.
3. Afterward, we’d have the students try some example problems. We’d discuss how to
solve a problem as a class, the goal of the discussion will be to ensure that students
realize that they have to solve in terms of the recessive allele, q, and work
backwards to get other values. Once that’s been ensured, we’d have students work
on other examples; initially individually, then in small groups, then we’d discuss the
examples as a class. Below are the formulas I referred to above.
Frequency of dominant allele = p
Raja Ali
Patrick Cole
Scott Housel
Page 6 of 8
EDU T&L 750
August 2, 2010
Hardy-Weinberg Equilibrium Lesson Plan
Grade 9-12
Frequency of recessive allele = q
Frequency of (counting) alleles
p+q=1
Square both sides:
(p

q
)2
1
2
2
p

2
pq

q

1
Frequency of (counting) individuals
p 2 = homozygous dominant
q 2 = homozygous recessive
2 pq = heterozygous
Application of Hardy-Weinberg Equilibrium (10 minutes):
1. This section will look at examples of the application of the Hardy-Weinberg
Equilibrium to the frequency of genetic disease. We'll use examples of real genetic
diseases and their probability within the population along with the Hardy-Weinberg
Equilibrium to determine the percentage of “carriers” in a given population. We'll
give the students two examples and ask them to use the equation that they learned
to find a percentage for the carriers.
2. We will ask: Given that the frequency of the cystic fibrosis allele (q) in the Caucasian
population is 2% (0.02), what is the percentage of carriers of the cystic fibrosis
gene? How do you arrive at your findings?
3. Students will use the equation to determine: Since p + q = 1 then p = 1 – 0.02 = 0.98.
The frequency of the "normal" allele (p) in the Caucasian population is therefore
98% (0.98). Since 2pq = frequency of heterozygote’s or carriers then in this example
2pq = 2 × 0.98 × 0.02 = 0.04. Students will determine that 1 in 25 Caucasians (0.04
 4%) are carriers of the cystic fibrosis gene.
4. Next, students will be introduced to PKU and asked to determine the carrier rate by
the following question: Phenylketonuria (PKU) is a human metabolic disorder that
results in mental retardation if it is untreated in infancy. In the United States, one
out of approximately 10,000 babies is born with the disorder. Approximately what
percent of the population are heterozygous carriers of the recessive PKU allele?
Raja Ali
Patrick Cole
Scott Housel
Page 7 of 8
EDU T&L 750
August 2, 2010
Hardy-Weinberg Equilibrium Lesson Plan
Grade 9-12
2
5. As before, students will use the equation to determine; q = 1/10,000 = 0.0001, so q
= 0.01, so p = 1 - q = 1 - 0.01 = 0.99. The carriers are heterozygous, therefore, 2pq =
2 (0.99) (0.01) = 0.0198  1.98%. Approximately 2% of the U.S. population carries
the PKU allele.
6. The students will then be asked: “So what? How can these findings be helpful?”
Students will be given the opportunity to share their ideas about the usefulness of
the Hardy-Weinberg Equation as it applies to genetic disease. Students should be
able to understand that this equation can apply to family, racial, and ethnic
backgrounds to give probabilities for babies to be born with these disorders within
various populations. This would allow couples within higher risk populations to be
tested to determine whether or not their children will be at risk for these disorders.
Final Turning Point “Clicker” Assessment (5 minutes)
Assessment/Evaluation
This lesson includes numerous opportunities for assessment and evaluation. There is
diagnostic assessment at the beginning of the lesson in the form of the “though-provoking
questions,” and the genetics review “clicker questions.” There is formative assessment in
the form of large group discussion and Q/A during the course of the lesson. And there is
formative/summative assessment at the end of the lesson in the form of questions
regarding the application of the Hardy-Weinberg Equilibrium, more “clicker questions,”
reviewing today’s new material, as well as a homework worksheet.
Raja Ali
Patrick Cole
Scott Housel
Page 8 of 8
EDU T&L 750
August 2, 2010
Hardy-Weinberg Equilibrium Lesson Plan
Grade 9-12
References Web Sites
Hardy-Weinberg practice. (n.d.). Retrieved from niceweb.com website:
http://bio1151.nicerweb.com/med/QUIZ/hw_q.html
Hardy-Weinberg Law. (n.d.). Retrieved from www.chsweb.lr.k12.nj.us website:
http://chsweb.lr.k12.nj.us/psidelsky/Law(HW).htm
Hardy-Weinberg Equilibrium. (n.d.). Retrieved from Department of Zoology, Oklahoma State
University website:
http://zoology.okstate.edu/zoo_lrc/biol1114/tutorials/Flash/life4e_15-6-OSU.swf
LabBench Activity - The Hardy-Weinberg Equation. (n.d.). Retrieved from Pearson Education
website:
http://www.phschool.com/science/biology_place/labbench/lab8/samprob1.html