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If sickle-cell anemia is so destructive why hasn't the sickle-cell allele been eliminated from the population?
Wiki User
∙ 14y ago
It is important to note that sickle-cell anemia comes in two forms. The homozygous sickle-cell anemia and the heterozygous sickle-cell trait. The difference between the two is that sickle-cell anemia has a high rate Death Rate at a young age (20~), and the sickle-cell trait is nearly asymptomatic.
In regions such as North America, sickle-cell anemia would be selected against and would eventually leave the gene pool. The sickle-cell trait on the other hand, has little effect on the fitness of the organism, and as such will remain in the gene pool.
In malaria endemic regions such as sub-Sahara Africa, sickle-cell anemia provides very high levels of immunity to malaria and the sickle-cell trait provides a slightly lesser level of immunity. Both forms of sickle-cell will increase the organisms fitness and as such, it will remain in the gene pool. Further on, the sickle-cell trait has greater fitness than sickle-cell anemia, hence, the sickle-cell trait will be selected as the fittest allele.
If s is the sickle-cell allele and S is a normal allele;
The relative fitness in malaria endemic regions;
Ss > ss > SS
Sickle-cell trait > Sickle-cell anemia > Normal
The relative fitness in non-malaria endemic regions;
SS > Ss > ss
Normal > Sickle-cell trait > Sickle-cell anemia
Wiki User
∙ 14y ago
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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.
If malaria were eliminated how might the frequency of the sickle-cell allele change over time?
Since people with the sickle cell allele trait are resistent to malaria, if malaria were eliminated there would be no change in the frequncy of sickle cell allele. This is because the presense of malaria does not have an affect on patients with the sickle cell allele trait.
Why might a harmful allele persist in a population for many generations?
A harmful allele may persist in a population due to genetic drift, where chance events can lead to its continued presence. Additionally, if the allele is recessive or has a late-onset effect, it may not be selectively disadvantageous enough to be eliminated by natural selection. Finally, a harmful allele may also persist if it is linked to a beneficial allele in the genome, creating a genetic trade-off.
What is allele fixation?
An allele present in all members of a population
What is a process that eliminated harmful allele from a gene pool?
negative selection.
Would a dominant allele ever return to a population?
If a population does not have a particular dominant allele, it could return to the population through the immigration of new individuals carrying the dominant allele.
What Is the percentage of a particular allele in a population?
Allele frequency.
What is a fixed allele.?
An allele present in all members of a population
What is the distribution of a particular allele within a population called?
Based on the Hardy-Weinberg Principle the rate at which a particular allele occurs in a population is its frequency.
How will the allele change in the rat population?
Evolution is the change in allele frequency over time in a population of organisms. Rats too!
What is an fixed allele APEX?
an allele present in all members of a population- APEX
What is a distribution of a particular allele within a population?
Based on the Hardy-Weinberg Principle the rate at which a particular allele occurs in a population is its frequency.
