Hardy-weinberg Equilibrium
Hardy-weinberg Equilibrium - Related Videos
06:19
Hardy-Weinberg and Genetic Drift - Concepts
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2019
Evolutionary change is interesting and important to study, but changes in populations occur over long periods of time and in huge physical spaces and are therefore very difficult to measure. In general, studying phenomena like this requires the use of mathematical models which are built using parameters that can be conveniently measured. These models are then used to make predictions about how changes to the system might affect the outcome. For example, changes to the frequency of genetic...
01:53
Hardy-Weinberg and Genetic Drift - Instructor Prep
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2019
Mathematical ModelingExpand Before beginning the mathematical modeling exercise make sure each computer has access to an either on or offline spreadsheet software program. Simulation for Hardy-Weinberg and Genetic DriftExpand Prepare one set of beads for each pair of students by counting out 50 of one color and then 50 of a second color, for a total of 100 beads. Then, place the beads in a paper bag. Students will also need extra beads to adjust the...
15:42
Hardy-Weinberg and Genetic Drift - Student Protocol
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2019
Class Simulation ExpandBegin by opening a new spreadsheet file. Following the Hardy-Weinberg equation where p is the frequency of a dominant allele A in a population, and q is defined as the frequency of a recessive allele B, input frequency p of allele A into cell B2, and frequency q of allele B into cell B3. Assign the value 0.5 to cell C2. Following the 1 – p = q equation, enter the formula “= 1 – C2” into cell C3 to calculate the frequency q of allele B. NOTE: Cells C2 and C3 will represent...
01:49
Hardy-Weinberg Principle
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2026
Diploid organisms have two alleles of each gene, one from each parent, in their somatic cells. Therefore, each individual contributes two alleles to the gene pool of the population. The gene pool of a population is the sum of every allele of all genes within that population and has some degree of variation. Genetic variation is typically expressed as a relative frequency, which is the percentage of the total population that has a given allele, genotype or phenotype.In the early 20th century,...
02:20
Dynamic Equilibrium
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2020
A reversible chemical reaction represents a chemical process that proceeds in both forward (left to right) and reverse (right to left) directions. When the rates of the forward and reverse reactions are equal, the concentrations of the reactant and product species remain constant over time and the system is at equilibrium. A special double arrow is used to emphasize the reversible nature of the reaction. The relative concentrations of reactants and products in equilibrium systems vary greatly;...
FAQs
The equation uses p and q for the frequencies of two alleles, then predicts homozygous frequencies as p² and q² and the heterozygous frequency as 2pq. The resulting values provide an expected genotype distribution that can be compared with population data, rather than treated as a description of every real population.
Each condition establishes a controlled baseline. Random mating affects how alleles combine, while a very large population limits changes associated with population size; excluding mutation, migration, and natural selection removes additional routes for allele frequencies to change. If one or more conditions is not met, a difference between expected and observed frequencies may reflect evolutionary forces rather than a calculation error.
A departure signals that the observed genotype pattern does not match the model’s expected distribution. Biologists can then consider nonrandom mating, gene flow, mutation, natural selection, or genetic drift as possible explanations. The comparison does not by itself identify which force acted; it directs attention toward the population process that could have altered allele or genotype frequencies.
They first determine allele frequencies in the population. Using those frequencies, they calculate expected genotype frequencies from p² + 2pq + q² = 1, then compare the predictions with observed data. Agreement supports use of the equilibrium baseline for that dataset, whereas a discrepancy highlights a possible departure and motivates examination of evolutionary forces or mating patterns.
It is useful when researchers need a reference point for judging whether genetic composition has changed. By contrasting predicted and observed genotype frequencies, they can detect patterns consistent with evolutionary change and frame questions about selection, migration, mutation, nonrandom mating, or drift. Its value lies in providing a simple baseline against which more complex population patterns can be interpreted.
In biology, the model links measurable genetic variation with population-level processes. Stable allele frequencies form the comparison point, while departures indicate that forces such as gene flow or natural selection may be influencing the population. This makes the principle useful for interpreting genetic data and distinguishing an unchanged distribution from a pattern that suggests evolutionary change.