456 CORRADO BAG LION I 



3. Ilb-Augustd I and Ilb-Augusta II 



Huisman (19(30) has reported the occurrence of a fast minor com- 

 ponent in the cord blood of Negro babies, together with Ilb-F, llb-A, 

 and Hb-S. Dissociation and recombination analysis of this minor com- 

 ponent, called Hb-Augusta I, showed the i)resence of (3^ chains only and 

 the structural formula /3.,^ was assigned to this hemoglobin. Family 

 studies showed the presence of minute amounts of Hb-H in one parent 

 and in some of the brothers of the propositus; it was concluded that 

 the formation of Hb-Augusta I (J3i^) was caused by a genotype. 



Preliminary evidence has been reported by iluisman (19(30j that a 

 different minor component observed in the cord blood of a baby, pre- 

 sumably heterozygous for the Hb-C gene and for a thalassemic gene 

 {a^^'/a^ l3^//3^), is made up of /?'' chains only; this ft/' liemoglobin has 

 been designated Hb-Augusta II. 



V. The Control of the Synthesis of Hemoglobin 



A. THE CONTROL OF THE RATE OF SYNTHESIS OF THE PEPTIDE CHAINS 



1. Rate of Synthesis of Normal Peptide Chains 



Approximately 95% of the red cell protein is hemoglobin. Tlie pep- 

 tide chains of hemoglobins are thus synthesized at a rate much higher 

 than that of any other protein in the red cells and the hemoglobin syn- 

 thesis is one of the main aspects of the differentiation of stem cells into 

 erythrocytes. Veiy little is known of the mechanisms controlling this 

 differentiation. One can guess that in the course of differentiation the 

 hemoglobin genes become activated in such a way that their products 

 become the main components of the I'ed cells; however, how the activa- 

 tion of a grouj) of genes is brought about selectively in mannualian 

 tissues is not known. 



In the normal red cells only "complete" hemoglobin molecules are 

 observed, i.e., Hb-A = a^.-^jS-^, Hb-F = ao/ y./, or Hb-A, = av^ 8,"^ These 

 hemoglobin molecules have in common a/'' dimers. During hemoglobin 

 synthesis the amount of jSo'^, y.''", and 8-^- dimers jjioduced is eriuivalent 

 to the amovmt of «., dimers produced. This raises the question of how 

 this equilibrium in the synthesis of ])roducts of independent genes is 

 maintained. It is known that when a defective a gene is present (as in 

 a chain thalassemia), abnormal aggregation of ^o or y... dimers may be 

 observed. It may thus be sujiposed tliat the (3 and y genes have an 

 autonomous regulation of (3 and y chain production. In pathological 

 conditions in whicli an equivalent amount of a cliains is not produced, 



