Q: A patient presents with mild anemia and splenomegaly. Laboratory tests reveal the presence of Hemoglobin C (HbC). Which amino acid substitution is responsible for HbC?

Glutamic acid to lysine at position 6 ($$\text{Glu} \rightarrow \text{Lys})$$

Q: Which mutation is responsible for the sickling phenomenon in sickle cell disease?

Beta-globin gene, codon 6, $$\text{GAG} \rightarrow \text{GTG} ($$glutamic acid to valine)

Question 1

Which of the following best describes the molecular basis of Hemoglobin E (HbE) mutation?

Accepted Answer

A point mutation at codon 26 of the beta-globin gene, changing glutamic acid to lysine ($$	ext{GAG} ightarrow 	ext{AAG})$$

Question 2

A patient presents with mild anemia and splenomegaly. Laboratory tests reveal the presence of Hemoglobin C (HbC). Which amino acid substitution is responsible for HbC?

Accepted Answer

Glutamic acid to lysine at position 6 ($$	ext{Glu} ightarrow 	ext{Lys})$$

Question 3

Which of the following statements about the inheritance of alpha-thalassemia is correct?

Accepted Answer

Alpha-thalassemia is inherited as an autosomal recessive disease

Question 4

A compound heterozygote with one HbS allele and one HbC allele will most likely:

Accepted Answer

Be asymptomatic unless a medical problem arises

Question 5

Which clinical manifestation is most commonly associated with HbS (sickle cell hemoglobin)?

Accepted Answer

Sickling of red blood cells due to decreased solubility

Question 6

A newborn in Southeast Asia is found to be homozygous for the HbE mutation. What is the most likely clinical outcome?

Accepted Answer

Asymptomatic or only mildly anemic

Question 7

Which of the following best explains why beta-thalassemia symptoms are generally more severe than alpha-thalassemia symptoms?

Accepted Answer

Excess alpha chains in beta-thalassemia are more toxic to red blood cells than excess beta chains in alpha-thalassemia

Question 8

Which mutation is responsible for the sickling phenomenon in sickle cell disease?

Accepted Answer

Beta-globin gene, codon 6, $$	ext{GAG} ightarrow 	ext{GTG} ($$glutamic acid to valine)

Question 9

A patient with beta-thalassemia major will most likely have which genotype?

Accepted Answer

Two mutant alleles with severe mutations

Question 10

Which of the following is a common treatment for beta-thalassemia major?

Accepted Answer

Regular blood transfusions and iron chelation therapy

Question 11

Hereditary Persistence of Fetal Hemoglobin (HPFH) is best described as:

Accepted Answer

A condition where fetal hemoglobin production continues into adulthood

Question 12

Which of the following is the most common structural hemoglobin variant worldwide?

Accepted Answer

Hemoglobin E (HbE)

Question 13

A patient with thalassemia trait (minor) is most likely to have:

Accepted Answer

Two deleted alpha-globin genes

Question 14

Which of the following best describes the pathogenesis of thalassemias?

Accepted Answer

Decreased synthesis of one or more globin chains, causing an imbalance in alpha and beta chain amounts

Question 15

A child born in India is diagnosed with severe anemia and is found to have thalassemia major. Which global health statistic is most relevant to this case?

Accepted Answer

More than 95% of severely affected infants are born in Asia, India, and the Middle East

Question 16

Which of the following hemoglobin mutations does NOT cause red blood cells to sickle?

Accepted Answer

HbC (beta 6, Glu to Lys)

Question 17

A patient with HbSC genotype is likely to have which of the following laboratory findings?

Accepted Answer

Hb levels near low normal values

Question 18

Which of the following is a direct consequence of decreased synthesis of alpha-globin chains in alpha-thalassemia?

Accepted Answer

Excess beta chains

Question 19

A mutation at codon 121 of the beta-globin gene results in which hemoglobin variant?

Accepted Answer

HbD

Question 20

Which of the following best explains the clinical variability seen in thalassemia phenotypes?

Accepted Answer

Severity depends on the class of mutation and gene dosage (heterozygous or homozygous)

Hemoglobinopathies: Structural Hb Variants, Thalassemias, and HPFH

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