 |  please explain the answer
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| Author | 8 Posts |
nadiabarati
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5. A 10-month-old boy with hemoglobin SS disease is brought to the emergency department by his parents because of severe pain in his feet for 2 hours. He appears acutely ill and is crying. Vital signs are normal except for a pulse of 160/min. Physical examination shows splenomegaly and edematous, tender feet. Laboratory studies show a hemoglobin concentration of 7 g/dL and a reticulocyte count of 12%. A peripheral blood smear shows target cells, poikilocytes, and sickled erythrocytes. Which of the following processes most likely caused the sickled erythrocytes in this patient?
A. Decreased interaction of hemoglobin S with spectrin upon deoxygenation
B. Inability of abnormal beta-chains to form tetramers upon deoxygenation
C. Inability of abnormal beta-chains to form tetramers upon oxygenation
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| doc179
Forum Guru
Topics: 67
Posts: 1,217
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This is what I found : Hb S arises from a mutation substituting thymine for adenine in the sixth codon of the beta-chain gene, GAG to GTG. This causes coding of valine instead of glutamine in position 6 of the Hb beta chain. The resulting Hb has the physical properties of forming polymers under deoxy conditions. It also exhibits changes in solubility and molecular stability. These properties are responsible for the profound clinical expressions of the sickling syndromes.
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| nida
Forum Elite
Topics: 23
Posts: 87
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There were some anwsers missing from your post:
A. Decreased interaction of hemoglobin S with spectrin upon deoxygenation
B. Inability of abnormal beta-chains to form tetramers upon deoxygenation
C. Inability of abnormal beta-chains to form tetramers upon oxygenation
D. Increased interaction of hemoglobin S with spectrin upon oxygenation
E. Spontaneous polymerization of hemoglobin S upon deoxygenation
F. Spontaneous polymerization of hemoglobin S upon oxygenation
destroy
I think the right anwser should be E)
It's abnormal hemoglobin polymerzaton during deoxygenation causing sickled RBC
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| nadiabarati
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Oh dear Nida, I got the Q from someone and it caused a headache for me and my friends! Thanks a lot. What is the source of Q? What is the meaning of oxygenation destroy in the last line?
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| nida
Forum Elite
Topics: 23
Posts: 87
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This is a NBME form 3Q.
F. Spontaneous polymerization of hemoglobin S upon oxygenation.
sorry about the word"destroy" I copied this from another form.
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| DrVirgo
Forum Hero
Topics: 1096
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whats the answer?
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| nadiabarati
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answer is E
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| DrVirgo
Forum Hero
Topics: 1096
Posts: 3,515
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WHY E? explanation?
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Our greatest glory is not in never falling, but in rising every time we fall.
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