Sickle Cell Disease is an Autosomal recessive disorder. The pathogenesis of the Glu to Val substitution. Decreases solubility of deoxygenated Hb. This causes a stiff fibrous polymers that distort RBCs giving a sickle cell shape. Sickle cell occludes the capillaries and cause __________ and __________.

platelets build up and clotting factors

Sickle cell can be detected in blood smears. Definitive diagnosis are made by __________

Hb electrophoresis showing high level of HbS > 80%

Hb electrophoresis showing low level of HbS < 80%

Compound heterozygote is 1 parent having HbS allele and other HbC allelle =

Sickle hemoglobin C disease (HbSC)

Hemoglobin Disease: Sickle Cell - Block 2 | Attempts: 354

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| By Jobusch

Jobusch

Community Contributor

Quizzes Created: 7 | Total Attempts: 17,050

Questions: 15 | Attempts: 354 | Updated: Mar 20, 2023

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Questions and Answers

1.

A Hemoglobin (Hb) molecule is a tetramer consisting of four polypeptide chains, 2 alpha and 2 Beta chains. Each Hb subunit contains a single heme moiety consisting of a protoporphyrin complexed with a single iron in order to bind oxygen.. Each heme can bind how many oxygen molecules and transport a total of ____ oxygen molecules.
- A.
  
  One: Two
- B.
  
  One: Four
- C.
  
  Two: Four
- D.
  
  Two: eight
Correct Answer
B. One: Four

Explanation
A Hemoglobin (Hb) molecule consists of four polypeptide chains, 2 alpha and 2 Beta chains. Each Hb subunit contains a single heme moiety, which is a protoporphyrin complexed with a single iron atom. Each heme can bind one oxygen molecule, and since there are four heme groups in a hemoglobin molecule, it can transport a total of four oxygen molecules.

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2.

The 5th week of gestation, hematopoeisis occurs in the ___________.
- A.
  
  Fetal liver and spleen
- B.
  
  Fetal spleen
- C.
  
  Fetal yolk sac
- D.
  
  Fetal bone marrow
Correct Answer
C. Fetal yolk sac

Explanation
During the 5th week of gestation, hematopoiesis, which is the formation of blood cells, occurs in the fetal yolk sac. This structure plays a crucial role in the early development of the embryo, providing nutrients and supporting the growth of the fetus. As the pregnancy progresses, hematopoiesis gradually shifts to other organs such as the liver and spleen, and eventually settles in the bone marrow. However, during the 5th week, the fetal yolk sac is primarily responsible for producing blood cells.

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3.

Up to the birth, hemoglobin is produced by __________.
- A.
  
  Fetal liver and spleen
- B.
  
  Fetal spleen
- C.
  
  Fetal yolk
- D.
  
  Fetal bone marrow
Correct Answer
A. Fetal liver and spleen

Explanation
During fetal development, the liver and spleen are responsible for producing hemoglobin. These organs play a crucial role in the production of red blood cells, including hemoglobin, which is responsible for carrying oxygen throughout the body. As the fetus grows and develops, the liver and spleen gradually decrease their role in hemoglobin production, and the responsibility is taken over by the bone marrow after birth.

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4.

After brith hemoglobin is produced in the bone marrow.
- A.
  
  True
- B.
  
  False
Correct Answer
A. True

Explanation
Hemoglobin is a protein found in red blood cells that is responsible for carrying oxygen throughout the body. After birth, hemoglobin is indeed produced in the bone marrow. The bone marrow is a soft, spongy tissue found inside bones, and it is responsible for producing red blood cells, including hemoglobin. Therefore, the statement is true.

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5.

Hemoglobin Fetal (2 alpha, 2 gamma HgF)) synthesis predominantly occurs during the fetal life and constitute 70% of total Hb at birth. Produced by fetus in utereo until about 48 weeks after birth. Has a high oxygen affinity oxygen delivering oxygen to the fetus. After brith, __________ production rapidly increases and HbF production drops off.
- A.
  
  Hemoglobin S
- B.
  
  Hemoglobin A
- C.
  
  Hemoglobin G
- D.
  
  Hemoglobin B
Correct Answer
B. Hemoglobin A

Explanation
Hemoglobin A (HbA): Adult, by 3months of age almost all the Hb is adult type

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6.

The changes in expression after birth, decreased expression gamma globin gene and concomitant expression of Beta globin gene is referred to as ____________.
- A.
  
  Upregulation globin
- B.
  
  Globin switch
- C.
  
  Beta switching syndrome
- D.
  
  Alpha elimination
Correct Answer
B. Globin switch

Explanation
After birth, there is a decrease in the expression of the gamma globin gene and a simultaneous increase in the expression of the beta globin gene. This change in expression is known as the "globin switch." It refers to the transition from the production of fetal hemoglobin (gamma globin) to adult hemoglobin (beta globin). This switch is essential for the proper functioning of red blood cells and is a normal developmental process that occurs after birth.

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7.

Variant is an Hb that contains a change. These can be benign or cause disease. Most variants result in a single aa substitution resulting from a point mutation.
- A.
  
  True
- B.
  
  False
Correct Answer
A. True

Explanation
The given statement is true. Variants are forms of a gene that contain a change, which can either be benign or cause disease. In most cases, variants lead to a single amino acid substitution due to a point mutation. This means that there is a change in the genetic code at a specific location, resulting in a different amino acid being incorporated into the protein.

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8.

Hemoglobin S (HbS) is on the Beta chain: residue 6 substituting a
- A.
  
  Glu to Lys
- B.
  
  Glu to Val
- C.
  
  Val to Glu
- D.
  
  Lys to Glu
Correct Answer
B. Glu to Val

Explanation
HBC is Glu to Lys on bet chain 6
HbF is Glu to Lys on beta chain residue 26
These changes lead to clinical manifestations

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9.

Hemoglobinopathies have two categories: Disorder of Hb structue and Hb synthesis.
- A.
  
  True
- B.
  
  False
Correct Answer
A. True

Explanation
Hb structure: Sickle cell disease
Hb synthesis: Thalassemias

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10.

Sickle Cell Disease is an Autosomal recessive disorder. The pathogenesis of the Glu to Val substitution. Decreases solubility of deoxygenated Hb. This causes a stiff fibrous polymers that distort RBCs giving a sickle cell shape. Sickle cell occludes the capillaries and cause __________ and __________.
- A.
  
  Ischemia and infractions
- B.
  
  Platelets build up and clotting factors
- C.
  
  Factor V and Plasminogen
Correct Answer
A. Ischemia and infractions

Explanation
The correct answer is "ischemia and infarctions". In sickle cell disease, the abnormal sickle-shaped red blood cells can block the small blood vessels, leading to decreased blood flow and oxygen supply to the tissues. This can result in tissue damage and ischemia (lack of blood flow) in various organs. Additionally, the blockage of blood vessels can also cause infarctions (tissue death) in the affected areas.

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11.

Irreversible sickled cells that are not removed by the spleen are removed by the liver.
- A.
  
  True
- B.
  
  False
Correct Answer
B. False

Explanation
Repeated sickling and unsickling produce irreversible sickled cells that are removed by the spleen. The rate of removal exceeds the production leading to anemia.

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12.

____________ is the major causes of death at all ages with sickle cell.
- A.
  
  Heart attack
- B.
  
  Infections
- C.
  
  Dehydration
- D.
  
  Albumin
Correct Answer
B. Infections

Explanation
Infections are a major cause of death at all ages with sickle cell. This is because individuals with sickle cell disease have a weakened immune system, making them more susceptible to infections. Infections can lead to complications such as pneumonia, meningitis, and sepsis, which can be life-threatening for individuals with sickle cell. Prompt and appropriate treatment of infections is crucial in managing sickle cell disease and reducing the risk of mortality.

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13.

Sickle cell can be detected in blood smears. Definitive diagnosis are made by __________
- A.
  
  Hb electrophoresis showing low level of HbS < 80%
- B.
  
  Hb electrophoresis showing high level of HbS > 80%
Correct Answer
B. Hb electropHoresis showing high level of HbS > 80%

Explanation
and via molecular biology: PCR analysis

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14.

Compound heterozygote is 1 parent having HbS allele and other HbC allelle =
- A.
  
  Sickle hemoglobin C disease (HbSC)
- B.
  
  Sickle B+ Thalassemia
- C.
  
  Sickle B* Thalassemia
- D.
  
  Sickel Hemoglobin SS disease
Correct Answer
A. Sickle hemoglobin C disease (HbSC)

Explanation
Sickle HbSC is usually milder in severity of the disease compared to HbSS.
Sickle B+ Thalassemia: the sickle cell allele inherited from one parent and the B allele from other parent.
Sickle B* Thalassemia: No production of Beta

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15.

B* Thalassemia has no beta globin expression.
- A.
  
  True
- B.
  
  False
Correct Answer
A. True

Explanation
B* Thalassemia is a genetic disorder that affects the production of hemoglobin, the protein responsible for carrying oxygen in the blood. In this condition, there is a mutation in the beta globin gene, leading to a decrease or absence of beta globin expression. As a result, the production of normal hemoglobin is impaired, causing anemia and other complications. Therefore, the statement that B* Thalassemia has no beta globin expression is true.

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Current Version
Mar 20, 2023

Quiz Edited by
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Mar 03, 2012

Quiz Created by
Jobusch

Hemoglobin Disease: Sickle Cell - Block 2

The 5th week of gestation, hematopoeisis occurs in the ___________.

Up to the birth, hemoglobin is produced by __________.

After brith hemoglobin is produced in the bone marrow.

The changes in expression after birth, decreased expression gamma globin gene and concomitant expression of Beta globin gene is referred to as ____________.

Variant is an Hb that contains a change. These can be benign or cause disease. Most variants result in a single aa substitution resulting from a point mutation.

Hemoglobin S (HbS) is on the Beta chain: residue 6 substituting a

Hemoglobinopathies have two categories: Disorder of Hb structue and Hb synthesis.

Irreversible sickled cells that are not removed by the spleen are removed by the liver.

____________ is the major causes of death at all ages with sickle cell.

Sickle cell can be detected in blood smears. Definitive diagnosis are made by __________

Compound heterozygote is 1 parent having HbS allele and other HbC allelle =

B* Thalassemia has no beta globin expression.