Student Exploration: Hardy-Weinberg Equilibrium

Student Exploration:Hardy-Weinberg Equilibrium

Student Exploration: Hardy-Weinberg Equilibrium
Directions: Follow the instructions to go through the simulation. Respond to the questions and
prompts in the orange boxes.

Vocabulary​:​ allele, genotype, Hardy-Weinberg equation, Hardy-Weinberg principle, heterozygous,
homozygous, incompletely dominant, Punnett square

Prior Knowledge Questions ​(Do these BEFORE using the Gizmo.)

1. A bird’s feather color is controlled by two ​alleles​, ​D​ (dark feathers) and ​d​ (lighter
feathers). Suppose two ​Dd​ birds mate. What percentages of ​DD​, ​Dd,​ and d ​ d
offspring would you predict? Use the ​Punnett square​ at right to help determine
your answer.

DD 25 Dd 50 dd 25

2. In this situation, what ratio of ​heterozygous​ (​Dd​) to ​homozygous​ (​DD​ and d
​ d)​ offspring would you expect
to find?

3:1


Gizmo Warm-up
Many factors—immigration, natural selection, hunting, etc—can influence the
composition of a population. To determine if one of these factors is affecting a
population, it is useful to know what a population looks like when ​none​ of these
factors is present.

In 1908, Godfrey Hardy and Wilhelm Weinberg independently discovered the laws that govern such
populations. These laws can be explored in the ​Hardy-Weinberg Equilibrium​ Gizmo.

1. The parrots you see represent a population of 500 parrots. For these parrots, the ​D​ allele is ​incompletely
dominant​ over ​d​, which means that ​Dd​ parrots are intermediate between ​DD ​and ​dd​ parrots. In the Gizmo,
select the TABLE tab. How many parrots of each ​genotype​ are in the initial population?


DD 250 Dd 100 dd 150


2. Return to the DESCRIPTION tab. Click ​Begin​, and then click ​Breed​. What happens?


The birds breed and lay eggs.


3. Click ​Hatch​, and look on the TABLE tab. What are the parrot populations now?

DD 184 Dd 223 dd 93



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, Activity A: Get the Gizmo ready​:

Alleles and ● On the DESCRIPTION tab, click ​Reset​.
genotypes ● Check that ​DD​ ​is 50% and ​dd​ is 30%.

Question: How will the proportion of genotypes and alleles change over time when mating is random
and no natural selection is occurring?

1. Predict​: How do you expect the proportions of ​D​ and ​d​ alleles to change over time?


I expect the overall population of the heterozygous parrots.


2. Gather data​: Run a generation in the Gizmo. After clicking ​Hatch​, fill in the allele and genotype
percentages for generation 1. Repeat this process for 5 generations.

Initial Generation
values 1 2 3 4 5
% ​D​ alleles 60 59 59.3 57.5 59.1 59.7
% ​d​ alleles 40 41 40.7 42.5 40.9 40.3
% of ​DD​ genotype 50 35.6 36.6 33.6 40.9 40.3
% of ​Dd​ genotype 20 46.8 45.4 47.8 47.8 48.2
% of ​dd​ genotype 30 17.6 18 18.6 17 16.2

3. Analyze​: What patterns do you see in your data?


The pattern is a decrease in the percentage of D alleles, an overall increase in the
percentage of D alleles, major decrease in the percentage of the DD genotype, major
increase in the percentage of the Dd genotype, decrease in the percentage of the dd
genotype.


4. Interpret​: Select the ALLELE GRAPH tab. What does this graph show?


this graph shows the allele percentage throughout each of the generations, showing both
the percentage of D alleles and d alleles expressed in 2 different colors.


5. Interpret​: Select the GENOTYPE GRAPH tab. What does this graph show?


the genotype graph shows the genotype percentage, giving all 3 types of possible
genotypes: DD, Dd, and dd.




Reproduction for educational use only. Public sharing or posting prohibited. © 2020 ExploreLearning™ All rights reserved