Certain alleles may cause serious diseases in a given environment but they may also be beneficial in different environmental conditions. It is a principle of natural selection.
Natural selection and alleles
Natural selection refers to the differential survival and reproduction of an organism in a given environment.
Certain alleles such as the allele of sickle cell disease show an evolutionary advantage in specific environmental conditions.
This allele is lethal in homo-zygous individuals, thereby tending to be eliminated from the population.
However, in regions where malaria is endemic, the presence of carriers individual having the sickle cell allele is advantageous to prevent this disease.
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