How does changing a nucleotide in the DNA code for b-globin change the characteristics of hemoglobin?

Due to change in nucleotide, a completely different protein is coded for. The normal protein has glutamic acid, is hydrophillic; however, the mutated protein incorporates valine, a hydrophobic amino acid instead.

This causes the overall haemoglobin protein to distort into a sickle shape, rather than a concave shape. As a result, sickle cells have a much shorter lifespan than their normal counterparts.