Question 1

Which of the following best explains why a single amino acid substitution in the β-globin subunit leads to sickle cell anemia?

Accepted Answer

It introduces a hydrophobic region that promotes abnormal aggregation of hemoglobin molecules.

Question 2

What is the quaternary structure of adult hemoglobin (HbA)?

Accepted Answer

Two α chains and two β chains

Question 3

During fetal development, which globin chains are predominantly expressed in hemoglobin?

Accepted Answer

α and γ chains

Question 4

Why does the sickle cell allele persist in populations where malaria is prevalent?

Accepted Answer

Heterozygous individuals have a survival advantage against malaria.

Question 5

Which of the following best describes the molecular change in sickle cell hemoglobin (HbS)?

Accepted Answer

A substitution of glutamic acid with valine at position 6 of the β-globin chain

Question 6

What is the primary physiological consequence of sickle-shaped red blood cells?

Accepted Answer

They block small blood vessels, leading to tissue damage.

Question 7

Which equation best represents the oxygen binding capacity of hemoglobin?

Accepted Answer

$$Hb + 4O_2 \rightarrow Hb(O_2$)_4$$

Question 8

A patient with sickle cell anemia is found to have a mutation in the β-globin gene. Which chromosome is this gene located on?

Accepted Answer

Chromosome 11

Question 9

Which of the following best explains the switch from fetal to adult hemoglobin after birth?

Accepted Answer

A gradual increase in β-globin gene expression and decrease in γ-globin gene expression

Question 10

Gene therapy for sickle cell anemia aims to:

Accepted Answer

Replace the mutated β-globin gene with a normal copy in hematopoietic stem cells

Question 11

Which of the following is a real-world consequence of sickle cell anemia in affected populations?

Accepted Answer

Reduced life expectancy due to organ damage from blocked blood vessels

Question 12

Which globin chain is NOT present in adult hemoglobin (HbA)?

Accepted Answer

γ chain

Question 13

If a population has a high frequency of the sickle cell allele, what can be inferred about the prevalence of malaria in that region?

Accepted Answer

Malaria is likely prevalent, providing a selective advantage for heterozygotes.

Question 14

Which of the following best describes the developmental pattern of globin gene expression?

Accepted Answer

Embryonic hemoglobin contains ε and ζ chains, fetal hemoglobin contains γ chains, and adult hemoglobin contains β chains.

Question 15

Which of the following is a plausible reason for the aggregation of sickle cell hemoglobin molecules?

Accepted Answer

Hydrophobic interactions between mutated β-globin subunits

Question 16

A patient is heterozygous for the sickle cell allele. What is their expected phenotype regarding sickle cell disease and malaria resistance?

Accepted Answer

They will be mostly healthy but have increased resistance to malaria.

Question 17

Which of the following best describes the role of zinc finger nucleases in gene therapy for sickle cell anemia?

Accepted Answer

They are used to specifically modify the mutated β-globin gene sequence in stem cells.

Question 18

Which of the following equations represents the genetic inheritance pattern of sickle cell anemia?

Accepted Answer

$$AA 	imes AS ightarrow 1/2 AA, 1/2 AS$$

Question 19

Which of the following statements about the switch from fetal to adult hemoglobin is correct?

Accepted Answer

The switch involves a decrease in γ-globin and an increase in β-globin expression.

Question 20

Which of the following is a direct effect of sickle cell hemoglobin on red blood cell morphology?

Accepted Answer

Red blood cells become rigid and crescent-shaped.

Hemoglobin Structure, Gene Expression, and Sickle Cell Anemia

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