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In any population of organisms you have variation, which means, to a greater or lesser extent, that allele frequencies are varied and great in number and not all of the organisms of the population possess the same alleles. Now some of those alleles confer reproductive advantage in the immediate environment. These organisms will be selected and the allele frequency possessed by these organisms will be the change in allele frequency that will show up in the populations gene pool.
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What condition would a mutation have the most impact on allele frequency?
A mutation would have the most impact on allele frequency in a condition where it confers a significant survival or reproductive advantage, such as in situations of strong natural selection or environmental change. For example, in a population facing a new disease, a mutation that grants resistance could rapidly increase in frequency. Additionally, if the mutation leads to a drastic change in phenotype that enhances mating success, it could also quickly alter allele frequencies through sexual selection. Overall, the strength of selection pressure and the context of the environment are critical in determining the mutation's impact.
What was primarily acting to change the frequency of the sickle-cell allele in the overall U.S. population?
The absence of the selection pressure malaria. Without selection, in the form of the malarial environment, the sickle cell allele will be lost in the overall US population. Even the heterozygous condition is somewhat deleterious and, statistically without malarial selection pressure the allele will be selected out.
The environment has changed and the frequency of the p allele has gone down what will this do to the q allele?
In a population's genetic makeup, if the frequency of the p allele decreases, it can lead to an increase in the frequency of the q allele if they are in a simple two-allele system (where p + q = 1). This is often the case in scenarios where the two alleles are in negative frequency-dependent selection, meaning that as one allele becomes less common, the other may benefit and increase in frequency. However, other factors such as selection pressures, mutation rates, and genetic drift can also influence the dynamics between p and q alleles.
What two factors could influence the alleles in a gene pool?
Two key factors that can influence the alleles in a gene pool are mutation and natural selection. Mutations introduce new alleles into a population, creating genetic variation. Natural selection can affect allele frequencies by favoring traits that enhance survival and reproduction, leading to an increase or decrease in certain alleles over time. Additionally, gene flow and genetic drift can also impact allele distribution within a population.
How is the sickle cell allele maintained through natural selection?
Individuals with two recessive alleles have very high rates of reproduction.
What condition would a mutation have the most impact on allele frequency?
A mutation would have the most impact on allele frequency in a condition where it confers a significant survival or reproductive advantage, such as in situations of strong natural selection or environmental change. For example, in a population facing a new disease, a mutation that grants resistance could rapidly increase in frequency. Additionally, if the mutation leads to a drastic change in phenotype that enhances mating success, it could also quickly alter allele frequencies through sexual selection. Overall, the strength of selection pressure and the context of the environment are critical in determining the mutation's impact.
What are the changes of allele frequency in a small population that is due to random chance and don't follow the laws of probability?
Random changes in allele frequency are due to genetic drift.
Does natural selection on single-gene trait cannot lead to changes in allele frequencies?
Natural selection acting on a single-gene trait can lead to changes in allele frequencies within a population. If individuals with a certain allele have a selective advantage, they are more likely to survive and reproduce, leading to an increase in the frequency of that allele in the population over time. This process is known as directional selection.
What effect does natural selection have on the frequency of a recessive lethal allele?
Perhaps not much as the recessive allele is masked in heterozygous condition. Depends on penetration and expresivity of the lethal allele, but any homozygous expression is fatal, so one can expect negative frequency selection; the freqiency is kept low by selection.
Why does selection act faster against a harmful dominant allele than a harmful recessive allele?
Selection acts faster against a harmful dominant allele because individuals with the allele will show the harmful trait, making them more likely to be removed from the population. In contrast, harmful recessive alleles are only expressed in homozygous individuals, making it harder for selection to act on them as carriers of the allele may not exhibit the harmful trait.
What is a process that eliminated harmful allele from a gene pool?
negative selection.
What is direct selection?
Directional selection is when natural selection favors a single phenotype. It occurs when there is a shift in population towards an extreme version of a beneficial trait.
What allele is responsible for maintaining sickle cell hemoglobin in African populations?
Balanced Selection
What was primarily acting to change the frequency of the sickle-cell allele in the overall U.S. population?
The absence of the selection pressure malaria. Without selection, in the form of the malarial environment, the sickle cell allele will be lost in the overall US population. Even the heterozygous condition is somewhat deleterious and, statistically without malarial selection pressure the allele will be selected out.
People with one sickle cell allele are not likely to get a malaria what is this an example of?
It is an example of Natural Selection, Modern Theories of Evolution.
Defective alleles are eliminated rapidly from population if they are?
A defective allele is more likely to be eliminated from a population if it is dominant. This is because it is immediately exposed to the effects of selection, as only one copy of a dominant allele is needed for it's characteristic to be developed. If an allele is recessive it can survive in a population as it is 'hidden' from selection by the presence of the corresponding dominant allele. It will only beexposed to selectionif an individual inherits the recessive allele from both parents. If the recessive allele is rare, the chances of two individuals with the allele mating could be quite small. In this way a defective recesssive allele could survive at low levels in a population.
What is the most likely cause of directional selection?
Homoygotes for one allele are favored over all others.
