Khanh Le - genetics paper

Khanh Le - genetics paper - those who are carriers of the...

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Khanh Le – Genetics paper Nov 7 th , 2011 When abnormal genes have benefits There are some genetic diseases, which should disappear or occur in small numbers, still remain in human population. Sickle cell anemia, Cystic Fibrosis, or PKU are some common examples that we have known so far about this issue. At first, it seems unreasonable for these diseases to keep occur among us. However, scientists have found out that it is “balanced polymorphism” that keeps these diseases “alive”. “Balanced polymorphism” is a special condition when a heterozygote for two alleles of a gene has some benefits to human beings in comparison to either of the homozygous states. For example, sickle cells are passed through generations because of its ability to resist malaria. Usually, for people with two abnormal copies of the hemoglobin gene (which causes sickle cell anemia), they will have to suffer serious “crisis” like pain, fever, etc. However, for
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Unformatted text preview: those who are carriers of the sickle cell trait, they do not suffer from malaria because the sickled cell and the parasite are filtered out by the spleen and destroyed. As a result, it is a big advantage for a community where malaria exists to have many carriers of sickle cell anemia. In the other hand, the chance that their children have this disease is also higher. The same process happens to people with Cystic Fibrosis (CF). People who have this disease will have thick and vicious secretions in their lungs, livers, etc. which stops them from normally develop like other people. However, when people only carry mutant CF alleles, they will have the ability to resist cholera. For this reason, CF alleles are still passed through generations. In brief, when heterozygote for two alleles of a gene gives human beings some advantages, natural selection will keep transmitting these alleles to our future generations....
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This note was uploaded on 12/11/2011 for the course BIO 100 taught by Professor Robinson during the Winter '08 term at BYU.

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Khanh Le - genetics paper - those who are carriers of the...

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