Chain of hemoglobin is 1 m. u. from the albino locus. assume for the moment that the same is true in humans. the disease sickle-cell anemia is the result of homozygosity for a particular mutation in the β-globin gene.

*Sickle cell disease is a constitutional corpuscular hemolytic anemia related to an abnormal structure of the globin chain. It is an autosomal recessive disease, which means homozygosity is necessary to fully express the illness.
*It corresponds to the synthesis of an abnormal hemoglobin, HbS, which is different from normal Hb (HbA).

*The S allele (located in the chromosome 11), responsible for the anomaly, is especially widespread in the African continent, it is also found in other regions of the Mediterranean.

*Mutation GAG to GTG leading to the substitution Glutamine by a valine in position 6 of the chain of the globine.

It allows water to resist freezing and thawing cycle.

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