Pathology Thread

The synthesis of the globin chains- a , b , d , e , g , and z , is controlled by structural genes on chromosomes 16 ( a ; z ) and 11 ( b , d , e , g ). The location and rate of synthesis varies from embryonic to fetal to neonatal to adult life.

Four polypeptide globin chains are arranged in pairs forming the tetrameric molecule or globin portion of hemoglobin. Each globin chain is covalently attached to a heme moiety.

The globin tetramer is globular or ellipsoid in shape, being approximately 550nm in diameter. The four porphyrin heme moieties lie in four regularly spaced clefts on the tetramer surface.

The globin portion of most normal hemoglobins consists of two chains from chromosome 16 and two from chromosome 11.

Normal a chains contain 141 amino acids; normal ß chains 146 amino acids. The d chain varies by 10 aa; the g chain by 39 aa compared with the ß chain.