The mRNA of beta-globin in sickle-cell hemoglobin substitutes valine (Val) for the wild-type glutamate (Glu) at codon 6.
What single-nucleotide change accounts for this Glu-to-Val substitution?
- A
Loss of the start codon.
- B
Insertion of an extra base, causing a frameshift.
- C
Methylation of histone H3 at the locus.
- Dcheck_circle
An A-to-T point substitution that changes GAG to GUG (in DNA: GAG to GTG).
Explanation
GAG (Glu) becomes GUG (Val) by substituting the middle A with U (DNA template change A->T). This single missense mutation in the beta-globin gene causes sickle-cell disease.