AbstractThe structural genes for the chains of hemoglobin control not only the amino acid sequence but also the net rate of synthesis of the chains. In some cases, high rate of destruction associated with a structural abnormality is an important factor in net synthesis. Balanced net production of α and β chains is probably maintained by selection against mutations that result in gross imbalance, since gross imbalance causes hemolytic anemia or death. Minor imbalances may be compensated for by destruction of excess chains without destruction of red blood cells. A proposed model for control of rate of synthesis of the globin chains postulates that completed chains are released from mRNA at a rate determined by the slowest step in their assembly. Decreased synthesis can result from a mutation that results in a slower step anywhere along the mRNA. On the other hand, increased synthesis can only result from a change in the specific position of the rate‐limiting s