A sample of 500 field mice contains 225 individuals that are D₁D₁, 175 that are D₁D₂, and 100 that are D₂D₂. Is this population in H-W equilibrium? Use the chi-square test to justify your answer.

Key Concepts

Hardy-Weinberg Equilibrium

The Hardy-Weinberg Equilibrium (HWE) is a principle that describes the genetic variation in a population that is not evolving. For a population to be in HWE, it must meet five conditions: no mutations, random mating, no natural selection, extremely large population size, and no gene flow. If these conditions are met, allele and genotype frequencies will remain constant from generation to generation.

Chi-Square Test

The Chi-Square Test is a statistical method used to determine if there is a significant difference between observed and expected frequencies in categorical data. In the context of genetics, it can be used to test whether the observed genotype frequencies in a population deviate from those expected under Hardy-Weinberg equilibrium. A high chi-square value indicates a significant difference, suggesting that the population may not be in equilibrium.

Genotype Frequencies

Genotype frequencies refer to the proportion of different genotypes within a population. In the given example, the frequencies of D₁D₁, D₁D₂, and D₂D₂ genotypes can be calculated from the sample size. These frequencies are essential for comparing observed data against expected frequencies under HWE, allowing researchers to assess whether the population is evolving or stable.