Question 1

Which of the following statements is true of the sickle cell trait-associated form of hemoglobin,Hb S?&#10;A) It is characterized by a relative deficiency of a chains versus b chains&#10;B) It has increased oxygen binding affinity relative to Hb A&#10;C) It is less soluble than Hb A&#10;D) It is dominant to Hb A&#10;E) Therapeutic approaches have been highly successful in alleviating phenotypes associated with Hb S

Accepted Answer

Hb S is less soluble than Hb A, leading to the formation of sickle-shaped red blood cells and subsequent health problems. A is false as Hb S has a relative substitution of valine for glutamic acid in the β-globin chain, not a chains versus b chains. B is also false as Hb S has decreased oxygen binding affinity compared to Hb A. D is false as Hb S is codominant with Hb A. E is partially false as therapeutic approaches have been somewhat successful but not highly successful in alleviating Hb S-associated phenotypes.

Question 2

Which of the following statements is true regarding the a1 and a2 globin chains?&#10;A) They are identical at the nucleotide and amino acid sequence level&#10;B) They differ at the nucleotide level but are identical at the amino acid level&#10;C) a1 pairs only with b1, and a2 pairs only with b2&#10;D) a1 is expressed in the fetus, and a2 is expressed after birth&#10;E) a2 is a pseudogene of a1

Accepted Answer

The a1 and a2 globin chains differ at the nucleotide level but are identical at the amino acid level. This means that although their DNA sequences are not the same, the differences do not change the amino acids for which they code, resulting in identical protein sequences.

Question 3

The complete absence of a globin production gives rise to which phenotype?&#10;A) Sickle cell disease&#10;B) Hb H disease&#10;C) b-thalassemia&#10;D) Hydrops fetalis&#10;E) Normal adult hemoglobin production

Accepted Answer

The complete absence of a globin production leads to hydrops fetalis, a severe form of anemia that is usually fatal in utero or shortly after birth. Sickle cell disease, Hb H disease, and b-thalassemia all involve either a deficiency or abnormality in globin production, but not a complete absence. Normal adult hemoglobin production is not affected by the absence of a globin production.

Question 4

The HbA form of hemoglobin consists of which globin chains?&#10;A) 1 a, 1 b&#10;B) 2 a, 2 b&#10;C) 2 a&#10;D) 2 a, 2 g&#10;E) 1 a, 1 g

Accepted Answer

The HbA form of hemoglobin consists of two alpha (α) and two beta (β) globin chains.

Question 5

This region regulates the switching of the b-like globin chains during development.&#10;A) Locus control region&#10;B) Master globin regulator&#10;C) Imprinting control region&#10;D) Globin switch&#10;E) Immediate early region

Accepted Answer

The locus control region (LCR) is a regulatory sequence that is responsible for coordinating the switching of globin genes during development. It is located upstream of the beta-globin cluster on chromosome 11 and is crucial for proper expression of the gamma-globin genes during fetal development, and the subsequent switching of gamma-globin to beta-globin in adults. Thus, the LCR acts as the master globin regulator, controlling the precise timing and expression of the globin genes.

Deck 10: Hemoglobin and the Hemoglobinopathies