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.
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Is balancing selection and stabilizing selection the same?
Balancing selection maintains genetic diversity in a population while stabilizing selection decreases genetic variation. Stabilizing selection favors a more uniform population, while balancing selection favors multiple alleles and non-uniform populations.
What type of selection is balancing selection?
Balancing selection describes the suite of adaptive forces that maintain genetic variation for longer than expected by random chance. It can have many causes, including heterozygous advantage, negative frequency-dependent selection, and environmental heterogeneity in space and time.
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 the same as disruptive selection?
A third category of selection (although not as frequently mentioned) is known as ‘disruptive selection’, which is essentially the direct opposite of balancing selection. In this case, both extremes of allele frequencies are favoured (e.g. 1 for one allele or 1 for the other) but intermediate frequencies are not.
Is balancing selection natural selection?
Balancing selection refers to forms of natural selection which work to maintain genetic polymorphisms (or multiple alleles) within a population. Balancing selection is in contrast to directional selection which favor a single allele.
What is balancing selection quizlet?
Balancing selection occurs when natural selection maintains two or more forms in a population. This type of selection includes heterozygote advantage and frequency-dependent 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 is potentially an important biological force for maintaining advantageous genetic diversity in populations, including variation that is responsible for long-term adaptation to the environment.
What is an example of stabilizing selection?
Stabilizing Selection When selective pressures select against the two extremes of a trait, the population experiences stabilizing selection. For example, plant height might be acted on by stabilizing selection. A plant that is too short may not be able to compete with other plants for sunlight.
What is balancing selection How does it act on populations?
Balancing selection refers to a number of selective processes by which multiple alleles (different versions of a gene) are actively maintained in the gene pool of a population at frequencies larger than expected from genetic drift alone. Balancing selection is rare compared to purifying selection.
What does balancing selection do to variation?
Balancing selection, on the other hand, brings the favored allele to an intermediate equilibrium, where it is maintained as a genetic polymorphism that potentially increases the variability in the genomic region nearby the selected locus.
What are the 3 types of selection?
There are three types of selection: Stabilising selection. Disruptive selection. Directional selection.
What are the three types of natural selection?
- Stabilizing Selection.
- Directional Selection.
- Disruptive Selection.
Does balancing selection reduce genetic variation?
By definition balancing selection encompasses all selective regimes that result in increased genetic diversity relative to neutral expectations.
How do stabilizing and disruptive selection differ?
Disruptive selection is a mode of natural selection which favours extreme values over intermediate values in a population. Stabilizing selection is a mode of natural selection which favours an average trait value over two extreme trait values.
Which type of selection is the most likely to result in speciation?
Natural selection can result in organisms that are more likely to survive and reproduce and may eventually lead to speciation.
Does stabilizing selection increase genetic variation?
Our results suggest that stabilizing selection depletes genetic variance in those trait combinations that are under the strongest selection and a lack of stabilizing selection on other trait combinations allows genetic variance to be maintained at much higher levels.
Is sickle cell An example of stabilizing selection?
Stabilizing selection – In this type the population stabilizes on a single non-extreme trait. It is the most common type of natural selection. It results in the decrease of population’s genetic variation. This type balances the two traits as in sickle cell anaemia which has two alleles.
What causes stabilizing selection?
Simply stated, there is no common cause of stabilizing selection, besides the fact that the most average individual is selected for. In that way, like all forms of selection, the cause of stabilizing selection is the increased fitness and reproductive success that the median individuals have.
What are the two ways of measuring genetic variation in a population?
Relative genotype frequency and relative allele frequency are the most important measures of genetic variation. Relative genotype frequency is the percentage of individuals in a population that have a specific genotype. The relative genotype frequencies show the distribution of genetic variation in a population.
Which of the following is a type of genetic drift?
There are two major types of genetic drift: population bottlenecks and the founder effect. A population bottleneck is when a population’s size becomes very small very quickly.
What is meant by stabilizing selection?
Stabilizing selection is the opposite of disruptive selection. Instead of favoring individuals with extreme phenotypes, it favors the intermediate variants. Stabilizing selection tends to remove the more severe phenotypes, resulting in the reproductive success of the norm or average phenotypes.
Is heterozygote advantage stabilizing selection?
Stabilizing selection occurs when heterozygous individuals are the most likely to survive. For that reason this fitness pattern is also referred to as heterozygote advantage.
Why is sickle cell anemia an example of balanced polymorphism?
Sickle Cell disease is an autosomal recessive disorder that causes anemia, joint pain, a swollen spleen, and frequent, severe infections. It illustrates balanced polymorphism because carriers are resistant to malaria, an infection by the parasite Plasmodium falciparum that causes cycles of chills and fever.