Student Exploration: Hardy-Weinberg Equilibrium
Vocabulary: allele, genotype, Hardy-Weinberg equation, Hardy-Weinberg principle, heterozygous, homozygous, incompletely dominant, Punnett square
Prior Knowledge Questions (Do these BEFORE using the Gizmo.)
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.
In this situation, what ratio of heterozygous (Dd) to homozygous (DD and dd) offspring would you expect to find?
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™.
The parrots you see represent a population of 500 parrots. For these parrots, the Dallele 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?
Return to the DESCRIPTION tab. Click Begin, and then click Breed. What happens?
Click Hatch, and look on the TABLE tab. What are the parrot populations now?
Alleles and genotypes
Get the Gizmo ready:
On the DESCRIPTION tab, click Reset.
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?
Predict: How do you expect the proportions of D and d alleles to change over time?
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.
Analyze: What patterns do you see in your data?
Interpret: Select the ALLELE GRAPH tab. What does this graph show?
Interpret: Select the GENOTYPE GRAPH tab. What does this graph show?