Sickle Cell Disease
By Levi Clancy for Student Reader on
updated
- Genetic disease
- Androgen Insensitivity
- Balanced Rearrangement
- Cancer genetics
- Chromosome Number Abnormalities
- Cystic Fibrosis
- Down Syndrome
- Duchenne Muscular Dystrophy
- Fragile X Syndrome
- Hemoglobinopathy
- Huntington Disease
- Hurler Syndrome
- Hyperphenylalaninemia
- Nondisjunction
- Penis-At-Twelve Syndrome
- Relative Risk
- Sickle Cell Disease
- Spinal Muscular Atrophy
- Tay-Sachs Disease
- Thalassemia
- Triplet Repeat Expansions
- Trisomy 13
- Trisomy 18
- Unbalanced Rearrangement
- Uniparental Disomy
- mRNA Splicing Aberrations
Sickle cell hemoglobin (HbS) results from a single nucleotide substitution which changes the codon of the sixth β-globin amino acid from glutamic acid to valine (GAG→GTG: Glu6Val) and is the causative agent of sickle cell disease when homozygous. Homozygotes have α2Aβ2S hemoglobin. Heterozygotes (said to have sickle cell trait) have α2Aβ2S (HbS), α2Aβ2A (HbA) and α2Aβ2Sβ2A (HbS/HbA hybrid) hemoglobin, and are clinically normal despite mild symptoms under low oxygen pressure. In Sickle Cell Disease, the HbS β chains form chains, aggregating into long fibers which deform the cell, impair its function and result in hemolysis for homozygotes.