Hardy Weinberg Practice Quiz

No mutation in the gene pool is one of the basic assumptions of the Hardy-Weinberg equilibrium. Other conditions include random mating, no migration, no selection, and a large population size.

Since allele frequencies must add up to 1, if p = 0.7 then q = 1 - 0.7 = 0.3. This ensures that the total frequency equals 1.

The Hardy-Weinberg principle states that genotype frequencies in a population can be represented as p², 2pq, and q², which sum to 1. This equation is fundamental for studying genetic variation in non-evolving populations.

In the Hardy-Weinberg model, an infinitely large population means genetic drift is negligible because random fluctuations in allele frequencies are minimized. This assumption helps maintain constant allele frequencies over generations.

Since q² = 0.16, taking the square root gives q = 0.4 and thus p = 0.6; therefore, the heterozygote frequency is calculated as 2pq = 2(0.6)(0.4) = 0.48 or 48%. This demonstrates how to derive genotype frequencies from observed phenotype proportions.

If 9% of the population expresses the recessive phenotype, then q² = 0.09. Taking the square root gives q = 0.3 and, using p + q = 1, we determine p = 0.7. This is a direct application of Hardy-Weinberg principles.

If 84% show the dominant phenotype, then 16% must be homozygous recessive, so q² = 0.16 and q = 0.4, with p = 0.6. The heterozygote frequency is calculated using 2pq, which equals 2(0.6)(0.4) = 0.48 or 48%. This follows the Hardy-Weinberg equation closely.

An increase in allele a will increase its frequency (q), and since genotype frequencies are determined by p², 2pq, and q², we expect q² (the frequency of homozygous recessives) to increase noticeably. Changes in allele frequency are immediately reflected in genotype proportions. This is the first observable impact in a Hardy-Weinberg population.

With q given as 0.2, we can calculate p as 0.8 since p + q = 1. The frequency of the homozygous dominant genotype is then p² = (0.8)², equaling 0.64 or 64% of the population. This is a standard calculation using Hardy-Weinberg assumptions.

In a large population, random genetic drift has little impact because fluctuations are averaged out. Thus, genetic drift is least likely to disturb allele frequencies compared to other forces like selection, mutation, or gene flow. This is a key assumption in Hardy-Weinberg equilibrium.

Given that 2pq = 0.48 and p + q = 1, solving the equation yields p = 0.6 and q = 0.4, or vice versa. This indicates that one allele is present at 60% and the other at 40% frequency. Such symmetry is typical in Hardy-Weinberg equilibrium calculations.

Introducing individuals with a high frequency of a recessive allele alters the overall allele frequencies in the population. This process is known as gene flow, where new genetic material is introduced. It can disturb the Hardy-Weinberg equilibrium by changing p and q.

A significant deficiency in heterozygotes compared to what is expected suggests that the population is not mating randomly or is affected by inbreeding. This is contrary to Hardy-Weinberg predictions, which assume a stable heterozygote frequency. Such deviations are strong indicators that the equilibrium conditions are not met.

Natural selection preferentially favors certain alleles over others, altering genotype frequencies from those predicted by Hardy-Weinberg equilibrium. This active selection disrupts the balance that is expected when evolutionary forces are absent. It is one of the primary mechanisms that can lead to evolutionary change.

The chi-square test is used to compare observed and expected frequencies to determine if deviations from Hardy-Weinberg equilibrium are statistically significant. It assesses whether any differences are due to chance or if other factors are at play. This test is a standard tool in population genetics research.

Using the Hardy-Weinberg formula 2pq with p = 0.8 and q = 0.2 gives 2(0.8)(0.2) = 0.32. Multiplying 0.32 by the total population of 1000 yields 320 heterozygotes. This calculation demonstrates the application of the principle to a known population size.

Non-random mating, such as inbreeding, increases the probability that individuals will inherit the same alleles from both parents. This results in an excess of homozygotes compared to the heterozygotes predicted by Hardy-Weinberg equilibrium. Observing such an excess is a strong indicator of non-random mating patterns.

Rapid shifts in allele frequencies over a few generations are most typically driven by strong natural selection. When certain genotypes confer a survival or reproductive advantage, they quickly become more common. This force can override the stable conditions assumed in the Hardy-Weinberg model.

A bottleneck significantly reduces the effective population size, violating the assumption of an infinitely large population. This leads to pronounced genetic drift and a departure from expected Hardy-Weinberg proportions. The assumption of a stable, large population is crucial to maintaining equilibrium.

When both gene flow and natural selection occur simultaneously, they interact to alter allele frequencies in complex ways. Such multiple evolutionary forces can combine to produce significant deviations from the stable genetic ratios predicted by Hardy-Weinberg equilibrium. This scenario shows that the equilibrium model can be disrupted by various interacting factors.