Sickle-cell anemia is caused by a point mutation in the -globin gene that results in which specific amino acid substitution at the sixth position of the -globin chain?
Answer and explanation
Correct answer: B. Substitution of Glutamic acid by Valine (GAG to GUG)
- Step 1: Sickle-cell anemia is an autosomal recessive molecular disease.
- Step 2: A single base transversion in the DNA template strand () causes the mRNA codon to change from to .
- Step 3: Consequently, the hydrophilic amino acid glutamic acid at the sixth position of the -globin chain is replaced by the non-polar hydrophobic amino acid valine, causing hemoglobin polymer aggregation under low oxygen tension.
Answer
Substitution of Glutamic acid by Valine (GAG to GUG).
Why not the others: Valine by Glutamic acid describes the reverse revertant back to wild-type; Lysine by Arginine does not occur in sickle-cell anemia; Glycine by Alanine is unrelated.
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