<prompt> In sickle cell anemia change in the amino acid isValine instead of glutamic acid in the 6th position of b chainGlutamic acid instead of valine in the 6th position of b chainValine instead of glutamic acid in the 6th position of a chainGlutamic acid instead of valine in the 6th position of a chain  <response>: A valine instead of glutamic acid in the 6th position of beta chain Molecular basis of Sickle cell hemoglobin: In case of sickle cell disease, the hemoglobin HbS has two normal a chains and two abnormal b chains. This is due to a difference in a single amino acid. In HbS, glutamate at 6th position b-chain of is replaced by valine. This occurs due to a change missense mutation in the single nucleotide thymine a adenine of the b globin gene. This error causes the formation of altered codon GUG in place of GAG which leads to the incorporation of valine at the 6th position. 