Question

I used to believe that there are good alleles and bad alleles and having two good alleles could never be worse than having one good and one bad allele.

However with sickle sell anemia having one good and one bad allele confers stronger immunity against malaria (though it can also cause hematuria and other generally undesirable outcomes).

Are there any other examples of this?

Answer 1

Another example of having one good allele and one bad allele conferring certain advantages is phenylketonuria (PKU). Heterozygous carriers of the PKU gene have no symptoms of the condition but can still pass on the mutated allele to their offspring.

Step-by-step explanation:

In addition to sickle cell anemia, another example where having one good allele and one bad allele can confer certain advantages is phenylketonuria (PKU). PKU is a genetic condition where individuals lack an enzyme responsible for converting harmful amino acids into harmless byproducts. If left untreated, PKU can lead to significant cognitive deficits and other health issues. However, individuals who are heterozygous carriers for PKU have one normal copy of the gene and one mutated copy, which allows for normal enzyme function and no symptoms. This means that these carriers have the advantage of not having PKU, while still potentially passing the mutated allele to their offspring.