What are examples of balancing selection?
The heterozygote is resistant to the malarial parasite which kills a large number of people each year. This is an example of balancing selection between the fierce selection against homozygous sickle-cell sufferers, and the selection against the standard HgbA homozygotes by malaria.
What do you mean by balancing selection?
Balancing selection means that two alleles are maintained in the population because of natural selection. This means that the fitness of an individual with two different versions of the allele is higher than the fitness of an individual with two copies of one of the alleles.
What are the two types of balancing selection?
Classic examples are known in humans and other organisms, and two different forms of balancing selection are very familiar—heterozygote advantage at a locus (often called overdominance), and frequency-dependent selection with a rare-allele advantage (although overdominance is often incorrectly used as synonymous with …
Is balancing selection positive selection?
The terms ‘positive selection’ or ‘positive Darwinian selection’ are often used to include both directional and balancing selection.
Which statement about balancing selection is correct?
Which statement about balancing selection is correct? ANSWER: When balancing selection occurs, all genotypes have equal or balanced biological fitness. When balancing selection occurs, certain alleles are favored when they are common, but not when they are rare.
Why is balancing selection important?
Balancing selection refers to a variety of selective regimes that maintain advantageous genetic diversity within populations. One shared feature of these mechanisms is that whether an allele is beneficial or detrimental is conditional on its frequency in the population.
Is balancing selection the same as disruptive selection?
Balancing selection keeps two or more alleles at intermediate frequencies and prevents fixation. Disruptive selection can fix either allele, if its frequency is already high enough.
What is balancing selection in evolution?
Balancing selection occurs when multiple alleles are maintained in a population, which can result in their preservation over long evolutionary time periods. A characteristic signature of this long-term balancing selection is an excess number of intermediate frequency polymorphisms near the balanced variant.
How does balancing selection differ from frequency dependent selection?
One type of balancing selection is the heterozygote advantage. Frequency-dependent selection is another type of balancing selection. This is when selection acts against a specific phenotype when it becomes too common. The phenotype that is less common often holds the advantage because it is less common.
How does balancing selection occur?
How does balancing selection work in natural selection?
Balancing selection. Balancing selection means that two alleles are maintained in the population because of natural selection. You would expect that one allele will provide higher fitness than the other, and therefore would outcompete the other allele. When there is balancing selection this does not happen, because the fitness is depended on…
How is balancing selection maintained in heterozygote advantage?
In heterozygote advantage, or heterotic balancing selection, an individual who is heterozygous at a particular gene locus has a greater fitness than a homozygous individual. Polymorphisms maintained by this mechanism are balanced polymorphisms.
How is the HgbS allele maintained through positive selection?
Maintenance of the HgbS allele through positive selection is supported by significant evidence that heterozygotes have decreased fitness in regions where malaria is not prevalent. In Surinam, for example, the allele is maintained in the gene pools of descendants of African slaves, as the Surinam suffers from perennial malaria outbreaks.
How does balancing selection work in a panmictic population?
All modern research has shown that this significant genetic variation is ubiquitous in panmictic populations. There are several mechanisms (which are not exclusive within any given population) by which balancing selection works to maintain polymorphism. The two major and most studied are heterozygote advantage and frequency-dependent selection.