Name: genetic drift simulation and hardy-weinberg lab prep
Uploaded: 2019-01-31T09:26:08.000Z
Duration: 1 min 53 s
Channel: JoVE

K12 Standards

ohios-learning-standards-and-model-curriculum

Ohio’s Learning Standards and Model Curriculum

9-12

Biology

Evolution

Mechanisms

Hardy-Weinberg and Genetic Drift

<ul><li><a href="#" data-time="7">Mathematical Modeling
</a></li><li><a href="#" data-time="21">Simulation for Hardy-Weinberg and Genetic Drift
</a></li></ul>

hardy-weinberg and genetic drift

<ol class="note-items">
	<li data-note-item="1" data-parent-collapse="">Mathematical Modeling<button class="expand">Expand</button>
	<ul class="lab-items">
		<li data-sub-note-item="1-1">
		<div class="lab-step">Before beginning the mathematical modeling exercise make sure each computer has access to an either on or offline spreadsheet software program.</div>
		</li>
	</ul>
	</li>
	<li data-note-item="2" data-parent-collapse="">Simulation for Hardy-Weinberg and Genetic Drift<button class="expand">Expand</button>
	<ul class="lab-items">
		<li data-sub-note-item="2-1">
		<div class="lab-step">Prepare one set of beads for each pair of students by counting out 50 of one color and then 50 of a second color, for a total of 100 beads.</div>
		</li>
		<li data-sub-note-item="2-2">
		<div class="lab-step">Then, place the beads in a paper bag.</div>
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		<li data-sub-note-item="2-3">
		<div class="lab-step">Students will also need extra beads to adjust the population makeup and these can be provided in a joint container for the whole class or instructors can make up additional sets for each student pair.</div>
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		<li data-sub-note-item="2-4">
		<div class="lab-step">Next, create slips of paper and write on these the different experimental scenarios that will test violations of the Hardy-Weinberg Equilibrium.</div>
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		<li data-sub-note-item="2-5">
		<div class="lab-step">Then, create a second set of paper slips to determine which genetic drift scenario the students will test.</div>
		</li>
		<li data-sub-note-item="2-6">
		<div class="lab-step">Finally, set out any additional beads needed for the experimental scenarios listed on the strips.</div>
		</li>
		<li data-sub-note-item="2-7">
		<div class="lab-step">NOTE: An additional 50 beads in a third color will be needed for the mutation violation, and an extra set of 100 beads in the first two colors for the gene flow scenario. For simulating the founder effect with 10 alleles and natural disaster with 10 alleles scenarios, randomly select 100 beads from 10 different colors.</div>
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	</ul>
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<div class="section-question"><h4 class="question-sect">What is the Hardy-Weinberg principle and why is it useful?</h4><p>The Hardy-Weinberg principle states that in absence of evolution, the allele frequencies of a population will stay the same over generations. This principle is used as a null model for population genetics and allows scientists understand evolutionary mechanisms.
</p></div><div class="section-question"><h4 class="question-sect">How is Hardy-Weinberg equilibrium calculated?</h4><p>Hardy-Weinberg equilibrium is calculated by mu...


	Mathematical ModelingExpand
	
		
		Before beginning the mathematical modeling exercise make sure each computer has access to an either on or offline ...

Education

JoVE Lab Manual

Lab Manual Sub Articles

genetic drift simulation and hardy-weinberg lab prep

<p class="jove_content">Genetic drift simulation and Hardy-Weinberg lab prep use beads and spreadsheet software to model changes in allele frequencies. Before starting the mathematical modeling exercise, make sure each computer has access to either online or offline spreadsheet software.</p>

<p class="jove_content">For the simulation, prepare one set of beads for each pair of students. Count out 50 beads of one color and 50 beads of a second color for a total of 100 beads, and place them in a paper bag. Students will also need extra beads to adjust the population makeup, and those can be kept in a shared class container or set up as additional bead sets for each pair.</p>

<p class="jove_content">Next, create paper slips that list the experimental scenarios used to test violations of Hardy-Weinberg equilibrium. Make a second set of slips to choose which genetic drift scenario the students will test. Set out any extra beads needed for those scenarios. A mutation violation needs 50 additional beads in a third color, and a gene flow scenario needs an extra set of 100 beads in the first two colors.</p>

<p class="jove_content">For the founder effect with 10 alleles and the natural disaster with 10 alleles, randomly select 100 beads from 10 different colors. This setup lets students compare how different population changes affect the model during the Hardy-Weinberg and genetic drift activity.</p>

Genetic Drift Simulation and Hardy-Weinberg Lab Prep

genetic-drift-simulation-and-hardy-weinberg-lab-prep

Allele Frequency Shifts in Small Populations

Allele frequency shifts in small populations can be explored with the Hardy-Weinberg equation and genetic drift. In this activity, students model how dominant and recessive alleles change from one generation to the next. They use both a spreadsheet simulation and a bead-based lab to track those changes over time.<br /><br />The spreadsheet model begins with p, the frequency of allele A, and q, the frequency of allele B. Students enter starting values, then use random formulas and a concatenate function...

Genetic drift simulation and Hardy-Weinberg lab prep use beads and spreadsheet software to model changes in allele frequencies. Before starting the mathematical modeling exercise, make sure each computer has access to either online or offline spreadsheet software.<br /><br />For the simulation, prepare one set of beads for each pair of students. Count out 50 beads of one color and 50 beads of a second color for a total of 100 beads, and place them in a paper bag. Students will also need extra beads to...

lab manual sub articles

Set up a Hardy-Weinberg and genetic drift simulation with beads, paper slips, and spreadsheet software. Includes mutation, gene flow, founder effect, and natural disaster scenarios.

Genetic Drift Simulation and Hardy-Weinberg Lab Prep | JoVE K12

Next Generation Science Standards

High School

Life Science

heredity-inheritance-and-variation-of-traits

Heredity: Inheritance and Variation of Traits

HS-LS3-3

Florida Department of Education

SC.912.L.15

SC.912.L.15.12

SC.912.L.15.14

new-york-state-science-learning-standards

New York State Science Learning Standards

Inheritance and Variation of Traits

HS-LS3-3.

Natural Selection and Evolution

HS-LS4-1.

HS-LS4-3.

Georgia Standards of Excellence

SB6.d

<p>Scientists once wondered why dominant traits like tan-colored giraffe spots do not become more frequent with each generation and replace recessive traits like dark brown spots. In thinking about this conundrum, in 1908, independent from each other, Godfrey H. Hardy and Wilhelm Weinberg independently derived a theory, today known as the Hardy-Weinberg Principle and represented by this equation. </p>
<p>The principle states that in the absence of evolution, i.e. at equilibrium, the allele and genotype frequencies of a population will remain constant from one generation to the next. To understand this equation, let&#39;s go back to the giraffe example. Uppercase A represents the tan allele since it is dominant, and lowercase a is for the brown allele because it is recessive. The frequency of these two alleles in the population are designated as p and q respectively. So how do we know the allele frequency? Well, each individual has two alleles. In this example, 40% of the alleles in the gene pool are tan. Thus, the frequency of the tan allele, p, is 0.4, and the frequency of the brown allele, q, is 0.6. Note that p plus q is always equal to one. </p>
<p>Now let&#39;s go back to the Hardy-Weinberg equation. Each term in the equation represents one genotype frequency. The frequency of the homozygous dominant genotype is p squared, and the homozygous recessive is represented by q squared. The heterozygous genotype is two pq. The reason we multiply by two here is that there are two different ways of generating a heterozygous genotype. Combined, these all represent 100% of genotypes. Thus, a total frequency of one. Using the values for p and q from our giraffe example, we can determine the genotype distribution of the color gene alleles in our giraffe population. Therefore, as per the Hardy-Weinberg Principle, at equilibrium, 16% of the giraffe population will be homozygous dominant, 48% will be heterozygous, and 36% are homozygous recessive. </p>
<p>To maintain this balance, the Hardy-Weinberg Equilibrium Principle states that a population should meet five main assumptions. There should be random mating, large population size, no mutation, no selection on the gene in question, and no gene flow in or out of the population. Most natural populations violate at least one of these assumptions and so equilibrium is rare&#8230;but in spite of this, the principle is used as a null model for population genetics. By comparing these expected values to the actual genotype frequency in a population, it can be determined whether that population is in Hardy-Weinberg Equilibrium. If not, then this means that some form of evolution or change in allele frequency is taking place. </p>
<p>A general misconception about evolution is that it requires natural selection to occur. However, this is not always the case. Genetic drift is one mechanism by which evolution can occur without natural selection. It is defined as a change in the allele frequency of a population due to chance. To envision this, let&#39;s go back to the example of a giraffe population and imagine their alleles of tan and brown being represented by marbles of two different colors. We will assume here that each color starts out equally abundant. If we were to start a new generation out of this population, we would need to breed pairs of individuals and thus select from four alleles per pair. If we select a breeding pair at random, then we might end up with two marbles of each color. However, by chance alone, some pairings will have only one color marble, or three of one color and one of the other. These chance deviations from 50-50 over multiple pairings to create a new generation might mean that the next generation no longer has an equal mixture of each allele. </p>
<p>It&#39;s this variation of relative allele frequencies over time that defines genetic drift. Therefore, unlike adaptive evolution, where allele frequency changes to select for traits that are fit for the environment, like ladybugs with a greater amount of melanin surviving better in colder climates because of an improved ability to absorb heat, genetic drift represents a type of evolution that is purely due to stochastic change. For example, the random removal of a section of a population through a catastrophic event. </p>
<p>In this lab, you will perform computer and colored bead simulations of Hardy-Weinberg Equilibrium and genetic drift in a population, and then test what happens when assumptions of the equilibrium are violated.</p>

hardy-weinberg tests for population change

<p class="jove_content">Hardy-Weinberg tests help scientists check whether a population is changing over time. Because evolution happens slowly and over large areas, researchers often use mathematical models to study it. These models use measurable data and computer simulations to predict how allele frequencies may shift across many generations.</p>

<p class="jove_content">The Hardy-Weinberg equilibrium equation is one common model. It was developed independently in 1908 by G. H. Hardy and Wilhelm Weinberg. The equation gives the expected allele frequency for a population that is not evolving, so it serves as a useful null hypothesis. If measured allele frequencies do not match the prediction, the gene may be undergoing evolutionary change.</p>

<p class="jove_content">The model is written as p2 + 2pq + q2 = 1. In this equation, p is the frequency of the dominant allele and q is the frequency of the recessive allele. The three terms represent the expected frequencies of the three diploid genotypes: homozygous dominant, heterozygous, and homozygous recessive. The allele version of the model is p + q = 1, since the two allele frequencies must total 1 in the population.</p>

<p class="jove_content">Hardy-Weinberg also depends on a set of assumptions. The population must be very large and closed, which means no individuals move in or out. There must be no mutations in the gene being studied. Individuals must mate at random, and natural selection must not be acting. When real data breaks one or more of these assumptions, the model can help point to what may be happening.</p>

<p class="jove_content">Genetic drift is one reason a small population can change by chance alone. This violates the large-population assumption of Hardy-Weinberg. One form of genetic drift is the founder effect. It happens when a small group leaves and starts a new isolated population. The genes carried by those founders shape future generations. In an extreme case, if the founders are all homozygous recessive, the dominant allele can disappear and the recessive allele can reach 100%.</p>

<p class="jove_content">A similar pattern is called the bottleneck effect. It can occur after a natural disaster, human intervention, or disease causes a major drop in population size. Genetic drift is not necessarily adaptive, because it does not specifically favor traits that fit the environment. Even so, it is an important evolutionary force in small populations and can create differences from Hardy-Weinberg predictions. In larger populations, those differences are more likely to suggest natural selection.</p>

<p class="jove_content">Scientists also use Hardy-Weinberg testing in modern studies of human and animal populations. One focus is how immune system genes relate to susceptibility to infectious disease. Researchers study genes such as CCR5 and the major histocompatibility complex, or MHC, called HLA in humans. By comparing genetic data with disease data, they can find patterns showing that some individuals are more resistant to certain infections while others are more likely to become ill. These studies have helped explain how infections have influenced evolution.</p>

Hardy-Weinberg Tests for Population Change

Evolutionary change is interesting and important to study, but changes in populations occur over long periods of time and in huge physical spaces and are ...

hardy-weinberg-tests-for-population-change

Test your understanding of Hardy-Weinberg and Genetic Drift with this Biology assessment quiz on JoVE Lab Manual. Covers key concepts through video-based questions designed to evaluate student learning.

Hardy-Weinberg and Genetic Drift - Assessment Quiz | JoVE Lab Manual

Model Hardy-Weinberg equilibrium, genetic drift, and allele frequency changes with spreadsheet and bead simulations in small and large populations.

Allele Frequency Shifts in Small Populations | JoVE K12

What is Natural Selection?

Natural selection is an evolutionary process in which individuals with survival-promoting traits reproduce at higher rates. These favorable traits become ...

Types of Selection

Natural selection influences the frequencies of particular alleles and phenotypes within populations in several different ways. Primarily, natural ...

Frequency-dependent Selection

When the fitness of a trait is influenced by how common it is (i.e., its frequency) relative to different traits within a population, this is referred to ...

Limits to Natural Selection

Organisms that are well-adapted to their environment are more likely to survive and reproduce. However, natural selection does not lead to perfectly ...

Natural Selection

Fitness
Widespread variation of phenotypes in natural populations provides the raw material for evolution, which is the change in the inherited traits of ...

Simulating Natural Selection
ExpandTo prepare for the lab, set out workstations for each student pair containing 6 white, 6 black, and 13 gray 12 inch ...

Simulating Natural Selection
ExpandTo begin, cut the white, black, and gray pipe cleaners into quarters, which should produce a total of 100 pieces that ...

Artificial Selection

Natural Selection and Adaptive Evolution
In natural settings, adaptive evolution takes place by natural selection, a process in which differences in ...

Observing Artificial Selection in Plants
ExpandTwo weeks before beginning the pollination experiments, collect a sufficient amount of small pots with a ...

Observing Artificial Selection in Plants 
ExpandTo begin the experiment, collect five two-week old grown plants from the generation one population that ...

What is Population Genetics?

A population is composed of members of the same species that simultaneously live and interact in the same area. When individuals in a population breed, ...

Hardy-Weinberg Principle

Diploid organisms have two alleles of each gene, one from each parent, in their somatic cells. Therefore, each individual contributes two alleles to the ...

Mutation, Gene Flow, and Genetic Drift

In a population that is not at Hardy-Weinberg equilibrium, the frequency of alleles changes over time. Therefore, any deviations from the five conditions ...

Genetic Drift

Natural selection&#x2014;probably the most well-known evolutionary mechanism&#x2014;increases the prevalence of traits that enhance survival and ...

Gene Flow

Gene flow is the transfer of genes among populations, resulting from either the dispersal of gametes or from the migration of individuals.

This ...

Class Simulation
ExpandBegin by opening a new spreadsheet file. Following the Hardy-Weinberg equation where p is the frequency of a dominant allele A in a ...

Mechanisms
• Natural selection
• Mutation
• Genetic drift
• Gene flow (immigration, emigration)
• Sexual selection

Content elaboration: Natural selection is used to describe the process by which traits become more or less common in a population due to consistent environmental pressures upon the survival and reproduction of individuals with the trait. Mathematical reasoning is applied to solve problems (e.g., use Hardy-Weinberg principle to explain deviations in observed gene frequency patterns in a population compared to expected patterns based on the assumptions of the principle). Populations evolve over time. Evolution through natural selection is the consequence of the interactions of:
1. The potential for a population to increase its numbers; 
2. The genetic variability of offspring due to mutation and recombination of genes; 
3. A finite supply of the resources required for life; and 
4. The differential survival and reproduction of individuals based on phenotype(s). 
Mutations are described in the content elaboration for Heredity. Apply the knowledge of mutation and genetic drift to real-world examples. Biological evolution explains the natural origins for the diversity of life. Emphasis shifts from thinking in terms of selection of individuals with a particular trait to changing proportions of a trait in populations as a result of the mechanisms of natural selection, genetic drift, movement of genes into and out of populations and sexual selection.

Taxonomy

Taxonomy is the science of defining and naming groups of biological organisms based on shared characteristics. It uses a hierarchy of increasingly ...

Phylogeny

Phylogeny is concerned with the evolutionary diversification of organisms or groups of organisms. A group of organisms with a name is called a taxon ...

evolutionary-relationships-through-genome-comparisons

Evolutionary Relationships through Genome Comparisons

Genome comparison is one of the excellent ways to interpret the evolutionary relationships between organisms. The basic principle of genome comparison is ...

Genome Copying Errors

DNA replication is a well-evolved process that copies millions of base pairs with high fidelity during each cell division. Occasionally a wrong base or a ...

Phylogenetic Trees

Synteny and Evolution

John H. Renwick first coined the term &#8220;synteny&#8221; in 1971, which refers to the genes present on the same chromosomes, even if they are not ...

Multi-species Conserved Sequences

Next-generation sequencing technologies have created large genomic databases of a variety of animals and plants. Ever since the human genome project was ...

Gene Duplication and Divergence

The seminal work of Ohno in 1970 popularized the idea of gene duplication and divergence. DNA sequence comparison studies reveal that a large portion of ...

Exon Recombination

The evolution of new genes is critical for speciation. Exon recombination, also known as exon shuffling or domain shuffling, is an important means of new ...

comparing-copy-number-variations-and-snps

Comparing Copy Number Variations and SNPs

Sequencing of the human genome has opened up several best-kept secrets of the genome. Scientists have identified thousands of genome variations that exist ...

Speciation
• Biological classification expanded to molecular evidence
• Variation of organisms within a species due to population genetics and gene frequency

Content elaboration: Biological classification expanded to molecular evidence
Classification systems are frameworks, developed by scientists, for describing the diversity of organisms; indicating the degree of relatedness among organisms. Recent molecular sequence data generally support earlier hypotheses regarding lineages of organisms based upon morphological comparisons. Both morphological and molecular comparisons can be used to describe patterns of biodiversity (cladograms present hypotheses to explain descent from a common ancestor with modification). The concept of descent from a common ancestor with modification provides a natural explanation for the diversity of life on Earth as partially represented in the fossil record and in the similarities of existing species. 
Variation of organisms within a species due to population genetics and gene frequency
Different phenotypes result from new combinations of existing genes or from mutations of genes in reproductive cells. At the high school level, the expectation is to combine grade 8 knowledge with an explanation of genes and the function of chromosomes. Natural selection works on the phenotype. Heritable characteristics influence how likely an organism is to survive and reproduce in a particular environment. When an environment changes, the survival value of inherited characteristics may change. This may or may not cause a change in species that inhabit the environment. Use real-world examples to illustrate natural selection, gene flow, sexual selection, and genetic drift.

Speciation

Genetic Drift Simulation and Hardy-Weinberg Lab Prep

Learning Objectives

What is the Hardy-Weinberg principle and why is it useful?

Lab Prep

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