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,
...
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 dd
offspring would you predict? Use the Punnett square at right to help determine
your answer.
2. In this situation, what ratio of heterozygous (Dd) to homozygous (DD and dd) offspring would you expect
to find?
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?
2. Return to the DESCRIPTION tab. Click Begin, and then click Breed. What happens?
3. Click Hatch, and look on the TABLE tab. What are the parrot populations now?
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DD 25 Dd 50 dd 25
3:1
DD 250 Dd 100 dd 150
The birds breed and lay eggs.
DD 184 Dd 223 dd 93
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 a
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