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Not an example. Read the trope description. This falls under Disability Immunity.
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* The prevalence of sickle cell disease (SCD) in African Americans and other populations with ancestry in malaria-endemic environments is an interesting example: while SCD is a notoriously debilitating and painful chronic disease linked to a recessive gene, research has shown that heterozygous carriers (that is, people with only one copy of the faulty gene instead of two) display some advantageous changes to their red blood cells. Instead of the 'sickle' deformation of SCD patients, carrier RBCs display very slight morphological changes proven to have resistance to the malaria parasite. Thus, there has been an evolutionary advantage conferred to the populations harboring the sickle cell gene in areas of the world with endemic malaria present. This offers an example of a "heterozygote advantage": a selective pressure existed to maintain the presence of a gene responsible for a disabling, life-shortening disease in the population because carriers of the gene have a significant survival advantage in their environment.
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* The prevalence of sickle cell disease (SCD) in African Americans and other populations with ancestry in malaria-endemic environments is an interesting example: while SCD is a notoriously debilitating and painful chronic disease linked to a recessive gene, research has shown that heterozygous carriers (that is, people with only one copy of the faulty gene instead of two) display some advantageous changes to their red blood cells. Instead of the 'sickle' deformation of SCD patients, carrier RBCs display very slight morphological changes proven to have resistance to the malaria parasite. Thus, there has been an evolutionary advantage conferred to the populations harboring the sickle cell gene in areas of the world with endemic malaria present. This offers an example of a "heterozygote advantage": a selective pressure existed to maintain the presence of a gene responsible for a disabling, life-shortening disease in the population because carriers of the gene have a significant survival advantage in their environment.
