All of the following are true about sickle cell anemia except (AIIMS May 2009)
|A|| Single nucleotide change leads to a change from glutamate to valine|
|B|| A single base pair change leads to RFLP|
|C|| Deoxygenated Hb leads to the exposure of sticky end.due to replacement of non polar residue by polar residue?|
|D||Offers protection to malaria in heterozygotes|
Genetics of Sickle Cell Anemia
a.The protein portion of hemoglobin consists of four globin subunits: two alpha (α) and two beta ().
a. These two types of subunits are encoded by the αand globin genes, respectively.
b. c. While the binding of oxygen actually occurs at the iron sites, all four globin chains must work together in order for the process to function well.
c. Sickle cell anemia, is caused by a point mutation in the globin gene.
d. As a result of this mutation, valine (a non-polar amino acid) is inserted into the globin chain instead of glutamic acid (an electrically charged amino acid).
e. That is a replacement of polar by non polar. The mutation causes the RBCs to become stiff and sometimes sickle-shaped when they release their load of oxygen.
f. The sickle cell mutation produces a "sticky" patch on the surface of the chains when they are not complexed with oxygen.
g. Because other molecules of sickle cell hemoglobin also develop the sticky patch, they adhere to each other and polymerize into long fibers that distort the RBC into a sickle shape.
h. The sickled cells tend to get stuck in narrow blood vessels, blocking the flow of blood. As a result, those with the disease suffer painful "crises" in their joints and bones.
i. They may also suffer strokes, blindness, or damage to the lungs, kidneys, or heart.
j. They must often be hospitalized for blood transfusions and are at risk for a life-threatening complication called acute chest syndrome.
k. Although many sufferers of sickle cell disease die before the age of 20, modern medical treatments can sometimes prolong these individuals lives into their 40s and 50s.