Homeostasis

"Sickle cell disease is an epitome of the mutual influences of the six levels of organizations of the human body on homeostasis. Indeed, sickle cell disease is a group of inherited red blood cell disorders harming the transportation of oxygen transferred from inhaled air, thanks to the respiratory system, to body cells through the cardiovascular system (Jurmain, Kilgore, & Trevathan, 2006). This pathology has been characterized by the proliferation of red blood cells presenting a sickle shape, i.e. a shape similar to the letter "C", whose detrimental effect has been to block the flow of blood in small blood vessels leading to the various tissues of organs (Jurmain, Kilgore, & Trevathan, 2006).

From the cell level point of view, sickle cell disease stemmed from a genetic mutation modifying the sequence of amino acids taking part in the production of an altered form of a protein known as haemoglobin S (HbS) at the root of the "C" shape of red blood cells (Jurmain, Kilgore, & Trevathan, 2006). This condition has exclusively originated from genetic inheritance, i.e. transmitted from parents to offspring on the form of a recessive allele (Jurmain, Kilgore, & Trevathan, 2006). Subsequently, genitors carrying this gene have contributed to giving birth to individuals whose genotype may be HbA / HbS (i.e. affected by a condition called "sickle-cell trait") or even HbS / HbS (i.e. suffering from sickle cell anaemia) (Jurmain, Kilgore, & Trevathan, 2006).

What is astonishing, at the very most, is that this harmful trait has propagated from West Africa to many areas in the world due to a zoonotic disease. As a matter of fact, specific environmental factors have played a prominent part in the process of natural selection, and its corollary adaptation, since at least about one thousand years (Currat et al., 2002). This dissemination, on the one hand, has sprung from the meeting of a pathogen agent and a vector, respectively the single-celled organism known as malaria, and...