Question 1

Which amino acid substitution is responsible for sickle-cell anemia in hemoglobin S?

Accepted Answer

Substitution of glutamic acid with valine at position 6 of the beta-globin chain

Question 2

What is the effect of the sickle-cell mutation on the properties of hemoglobin?

Accepted Answer

It makes hemoglobin more hydrophobic, causing aggregation under low oxygen conditions

Question 3

Which of the following best explains why sickle-cell anemia leads to a low red blood cell count?

Accepted Answer

Sickled cells are more prone to hemolysis due to their abnormal shape

Question 4

Which of the following is a consequence of the sickle-cell mutation at the DNA level?

Accepted Answer

A single nucleotide substitution from A to T in the beta-globin gene

Question 5

Why does the sickle-cell trait confer resistance to malaria?

Accepted Answer

Heterozygous individuals have red blood cells that are less hospitable to Plasmodium parasites

Question 6

Which of the following best describes the change in hemoglobin's properties due to the sickle-cell mutation?

Accepted Answer

Hemoglobin becomes less soluble and more likely to aggregate under low oxygen conditions

Question 7

A patient with sickle-cell anemia is found to have a mutation in the beta-globin gene. Which codon change is most likely responsible?

Accepted Answer

GAG to GTG

Question 8

In an electrophoresis experiment, which hemoglobin variant migrates farther toward the positive electrode at pH 8.6?

Accepted Answer

Normal adult hemoglobin (HbA)

Question 9

Which of the following statements about sickle-cell anemia is TRUE?

Accepted Answer

It is caused by a point mutation in the beta-globin gene

Question 10

Which property of valine, substituted for glutamic acid in sickle-cell hemoglobin, contributes to the disease phenotype?

Accepted Answer

Valine is nonpolar and hydrophobic, promoting aggregation of hemoglobin molecules

Question 11

Which of the following is NOT a physiological effect of sickle-cell anemia?

Accepted Answer

Increased red blood cell count

Question 12

A researcher is analyzing the DNA sequence of a patient with sickle-cell anemia. Which sequence would they most likely find in the beta-globin gene?

Accepted Answer

$$	ext{GUG}$$

Question 13

Which of the following best explains the molecular basis for the sickling of red blood cells in sickle-cell anemia?

Accepted Answer

Hydrophobic interactions between hemoglobin S molecules cause polymerization under low oxygen conditions

Question 14

Which of the following is a common misconception about sickle-cell anemia?

Accepted Answer

Heterozygous individuals (carriers) always show symptoms of the disease

Question 15

Which of the following statements about the inheritance of sickle-cell anemia is correct?

Accepted Answer

It is inherited in an autosomal recessive manner

Question 16

A patient with sickle-cell anemia is found to have decreased oxygen affinity in their hemoglobin. Which molecular change is most responsible for this?

Accepted Answer

Substitution of a hydrophobic amino acid (valine) for a hydrophilic one (glutamic acid)

Question 17

Which laboratory test is commonly used to distinguish between HbA and HbS in patients suspected of having sickle-cell anemia?

Accepted Answer

Hemoglobin electrophoresis at alkaline pH

Question 18

Which of the following is a direct result of the sickle-cell mutation in hemoglobin?

Accepted Answer

Formation of long, rigid polymers of hemoglobin under low oxygen conditions

Question 19

Which of the following best describes the evolutionary significance of the sickle-cell trait?

Accepted Answer

It provides a selective advantage in regions where malaria is endemic

Sickle-Cell Anemia: Molecular Basis, Physiological Effects, and Evolutionary Implications

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