Sickle-cell disease results from a point mutation in the second nucleotide of the codon GAA, changing it to GUA. This results in a change in the amino acid at position 6 in the hemoglobin protein. This solution shows the effect that this mutation would have on the amino acid encoded by this codon, using as an example an RNA molecule consisting of multiple repeats of the relevant codons. The effects of reading these RNA molecules in different reading frames is also illustrated.