# hardy weinberg theorem

## hardyweinberg equilibrium

Sometimes understanding how common a gene is within a population is necessary. Or, more specifically, you may want to know how common a certain form of that gene is within the population, such as a recessive form. This can be done using the Hardy-Weinberg model, but it can only be done if the frequencies of the genes are not changing. The Hardy-Weinberg model describes how a population can remain at genetic equilibrium, referred to as the Hardy-Weinberg equilibrium. Genetic equilibrium occurs when there is no evolution within the population. In other words, the frequency of alleles (variants of a gene) will be the same from one generation to another. At genetic equilibrium, the gene or allele frequencies are stablethey do not change. For example, lets assume that red hair is determined by the inheritance of a gene with two allelesR and r. The dominant allele, R, encodes for non-red hair, while the recessive allele, r, encodes for red hair. If a populations gene pool contains 90% R and 10% r alleles, then the next generation would also have 90% R and 10% r alleles. However, this only works under a strict set of conditions. The five conditions that must be met for genetic equilibrium to occur include: 1. 2. 3. 4. 5. No mutation (change) in the DNA sequence. No migration (moving into or out of a population). A very large population size. Random mating. No natural selection. These five conditions rarely occur in nature. When one or more of the conditions does not exist, then evolution can occur. As a result, allele frequencies are constantly changing, and populations are constantly evolving. As mutations and natural selection occur frequently in nature, it is difficult for a population to be at genetic equilibrium. The Hardy-Weinberg model also serves a mathematical formula used to predict allele frequencies in a population at genetic equilibrium. If you know the allele frequencies of one generation, you can use this formula to predict the next generation. Again, this only works if all five conditions are being met in a population.

## instructional diagrams

No diagram descriptions associated with this lesson

## questions

at genetic equilibrium, there is no evolution.

``````-->  a. true

b. false
``````

genetic equilibrium rarely occurs in nature.

``````-->  a. true

b. false
``````

which of the following are conditions for hardy-weinberg equilibrium?

``````a) no mutations

b) no natural selection

c) random mating

-->  d) all of the above
``````

which of the following processes selects for specific alleles?

``````-->  a) natural selection

b) random mating

c) large population

d) migration
``````

the movement of 100 individuals into an area each winter, and the movement of 50 out of the area each spring is an example of

``````a) natural selection.

b) random mating.

-->  c) migration.

d) mutation.
``````

if a population at genetic equilibrium consists of 75% a alleles one generation, how many a alleles will be in the population the next generation.

``````a) 75%

b) 50%

-->  c) 25%

d) 0%
``````

if a population consists of 10% recessive aa phenotype, what amount of the population has the dominant phenotype?

``````a) 10% aa

b) 80% aa

-->  c) 90%

d) all of the above
``````

## diagram questions

No diagram questions associated with this lesson