What is balanced polymorphism?

[rak173]

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I have seen many definitions online but couldn't really understand. Can someone explain in simple words? How does balanced polymorphism differ from polymorphism? Thanks.

 

[ncide]

Balanced polymorphism is when there are selective pressures that select for an array of alleles in a balanced fashion.

An example would be sickle cell disease and malaria. Homozygosity for the diseased alleles leads to sickle cell disease, which is deleterious, however, the environment still selects for the allele because it confers resistance to malaria. People who do not have both alleles but have one have a less severe disease, and are resistant to malaria, so the disease phenotype exists and is balanced with the healthy phenotype.

 

[rak173]

Balanced polymorphism is when there are selective pressures that select for an array of alleles in a balanced fashion.

An example would be sickle cell disease and malaria. Homozygosity for the diseased alleles leads to sickle cell disease, which is deleterious, however, the environment still selects for the allele because it confers resistance to malaria. People who do not have both alleles but have one have a less severe disease, and are resistant to malaria, so the disease phenotype exists and is balanced with the healthy phenotype.

So it is same as Heterozygote Advantage?

 

[ncide]

Heterozygote advantage is just what it means. An advantage conferred to the members who are heterozygous for a trait. It results in balanced polymorphism since you have an array of alleles present (there will always be homozygous members with recessive and dominant alleles because of the heterozygotes).

 

[DAT Destroyer]

I have seen many definitions online but couldn't really understand. Can someone explain in simple words? How does balanced polymorphism differ from polymorphism? Thanks.

Balanced polymorphism could be viewed as a type of a Heterozygous advantage. You basically have 2 different versions of the gene where neither version has superiority. Sometimes it is carefully maintained in population because individuals with 2 different versions of that gene have a higher fitness rate than individuals that have only one version. Sickle cell anemia and liver enzymes are good examples.
It is maintained in certain environments in order to increase the survival rate.

Hope this helps.

 

[rak173]

Heterozygote advantage is just what it means. An advantage conferred to the members who are heterozygous for a trait. It results in balanced polymorphism since you have an array of alleles present (there will always be homozygous members with recessive and dominant alleles because of the heterozygotes).

Thanks. Is there any difference between balanced polymorphism and just polymorphism?

 

[aceofbass]

Thanks. Is there any difference between balanced polymorphism and just polymorphism?

balanced means that the array of possible phenotypes is "balanced" because of selective pressure. Polymorphisms just mean that there are multiple phenotypes in the wild