(4) Consequence of base substitution mutation

Even a small change in bases can result in mutation for example the gene that controls sickle-cell anemia where a change of only one base leads to a protein with one amino acid changing resulting in sickle-cell anemia.

Hemoglobin is made of 4 polypeptide chains: two alpha and two beta.

When an A to T base substitution occurs in the region of the gene coding for the 6^th amino acid in the beta chain the codon GAG (glutamic acid) becomes GTG (valine)

The resulting polypeptide is different and the hemoglobin formed is commonly known as HbS: the “normal” hemoglobin is known as HbA

HbS is a slightly different structure: one amino acid makes it crystallize at low…