The iron is transported to the bone marrow to be incorporated in the hemoglobin of newly formed erythrocytes. The hemoglobin concentration of blood varies with the hematocrit. There are six different types of globin chains, designated by the Greek letters alpha, beta, gamma, delta, epsilon, and zeta. The chains are coded by different genes, which are turned on and off during development in order to produce hemoglobins with the oxygen-carrying properties required at each developmental stage. Many abnormal hemoglobins arising from mutations have been discovered.
Some mutations result in a reduced rate of hemoglobin synthesis.
All such conditions are known as hemoglobinopathies. They can result from deletion of the gene for a chain or from a mutation in the regulatory gene that controls the synthesis of the chain. All rights reserved.