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