Health Sciences & Medicine
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Sickle-cell anemia is a term that denotes a group of genetic disorders caused by sickle shaped hemoglobin Hgb S or Hb S. In patients with this disease the human red blood cells take a different shape upon deoxygenation because of polymerization of the abnormal sickle hemoglobin.


Sickle-cell anemia is common in population in Saharan Africa and their descendants from parts of the world. Sickle-cell disease can occur in any individual of any race or ethnicity across the globe."Sickle-cell anemia" is a specific form of sickle-cell disease caused by a homozygous mutation forming Hgb S. Other forms of sickle-cell disease include sickle-haemoglobin C disease,sickle beta-plus-thalassemia,sickle beta-zero-thalassemia and hemoglobin ss causesd by heterozygous genes (Orah , 2000)..The origin of the mutation that led to the sickle cell gene was initially thought to be in the Arabian region spreading to Asia and Africa. It is now confirmed from evaluation of chromosome structures that there should have been at least four independent mutational events spanning over 70000 to 150000 years, three in Africa and a fourth in either Saudi Arabia or central India.The evolution of sickle-cell anaemia is understood and explained as an example of Baldwinian phylogeny whereby humans modify their environment and thus change the selective pressures.
Patients with sickle cell anaemia exhibit anaemia with typical hemoglobin levels of 6-9 g/dl. ...
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