Each amino acid is coded for by a sequence of three bases. The gene for the beta chain contains the code for a sequence of 146 amino acids. The first six of these amino acids are: valine, histidine, leucine, threonine, proline , and glutamic acid.
The specific base sequence for these amino acids is: GTG/CAC/CTG/ACT/CCT/GAG.
Normal Human Beta Chain (first six codons)
| Val | His | Leu | Thr | Pro | Glu |
| GTG | CAC | CTG | ACT | CCT | GAG |
Sickle cell hemoglobin (Hemoglobin S) results when, glutamic acid that is normally present in the sixth position on the beta globin chain is substituted with valine.
Sickle Cell Hemoglobin (first six codons)
| Val | His | Leu | Thr | Pro | Val
|
| GTG | CAC | CTG | ACT | CCT | GTG
|
"ß6glu-val" in the nomenclature indicates this mutation in the sixth position on the beta chain.
