5. Protein Structure & Function – Hemoglobinopathies & Anemia Vocabulary

Vocabulary flashcards summarizing key terms, mutations, and disease phenotypes related to hemoglobin structure, function, and associated anemias.

Anemia

A condition characterized by an insufficient number of healthy red blood cells or the presence of abnormal hemoglobin.

Normal Hemoglobin Range

13.5–17.5 g/dL in men, 11.5–16 g/dL in women, and 14–20 g/dL in infants.

Hemoglobinopathy

Any genetic disorder of hemoglobin structure, production, or subunit association that results in anemia.

Structural Hemoglobin Defect

Disease caused by a point mutation that replaces one amino acid in a globin chain, altering hemoglobin function (e.g., HbS, HbC).

Synthesis (Production) Defect

A mutation that lowers synthesis of one globin chain, creating an imbalance and resulting in thalassemia.

Abnormal Subunit Association

Lack of one globin chain forces identical chains to tetramerize, producing non-functional hemoglobin (e.g., α-thalassemia).

Hemoglobin A (HbA)

Normal adult hemoglobin composed of two α and two β chains (α2β2).

Hemoglobin A2 (HbA2)

Minor adult hemoglobin (<3%) consisting of two α and two δ chains (α2δ2).

Hemoglobin F (HbF)

Fetal hemoglobin with two α and two γ chains (α2γ2); predominant before birth.

Hemoglobin S (HbS)

Variant with β-chain mutation Glu6→Val; forms a2βS2 and causes sickle cell disease.

Sickling Electrophoresis Test

At alkaline pH, HbS migrates more slowly toward the anode than HbA because it is less negatively charged—used diagnostically.

Sickle Cell Trait

Heterozygous state (one HbS, one normal β gene) that is usually benign.

Sickle Cell Anemia

Homozygous HbS disease marked by painful crises, hemolytic anemia, hyperbilirubinemia, infection risk, and RBC lifespan <20 days.

Hemoglobin C (HbC)

β-chain mutation Glu6→Lys; produces mild hemolytic anemia and splenomegaly (a2βC2).

Hemoglobin E (HbE)

β-chain mutation Glu26→Lys triggering alternate splicing; causes mild β-thalassemia phenotype common in Southeast Asia.

Hemoglobin Constant Spring

Mutation elongating the α chain; unstable mRNA and protein create a thalassemic phenotype.

Hemoglobin H Disease

α-thalassemia intermedia with deletion of three α genes; tetramer of β chains (β4) leads to microcytic hypochromic hemolytic anemia.

Hemoglobin Bart Syndrome

Severe α-thalassemia (hydrops fetalis) with γ4 tetramers; usually results in stillbirth or early neonatal death.

β-Thalassemia Major

Near-complete absence of β-chain production causing severe anemia and transfusion dependence.

β-Thalassemia Intermedia

Partial reduction of β-chain synthesis producing moderate anemia.

Point Mutation

Single nucleotide substitution in DNA leading to one amino acid change in a protein.

Hyperbilirubinemia

Elevated bilirubin level in blood, commonly seen in chronic hemolytic anemia such as sickle cell disease.