The nucleotide triplet CTC in the sixth position of the l3-chain in DNA forms the complementary nucleotide on (mRNA) that codes for glutamic acid. A point mutation on the l3-chain resulting in the nucleotide triplet CAC forms a complementary nucleotide on mRNA that codes for valine. In sickle cell anemia, you would expect the complementary nucleotide triplet on mRNA from 5&; to 3&; to read
Note that by changing the CTC triplet to a CAC, the messenger RNA (mRNA) changes from GAG, which normally codes for glutamic acid in the sixth position of the -chain of hemoglobin, to GUG, which now codes for valine. This point mutation of a single base pair is responsible for sickle cell anemia. Ref : Biochemistry by U. Satyanarayana 3rd edition Pgno : 202,203
GAG
CTC
GTG
GUG
Structure and function of protein