Hemoglobin patterns were examined in human fetuses in order to determine the onset of synthesis of adult hemoglobin in fetal red cells. In fetuses younger than 11 gestational wk, hemoglobin A could not be detected with electrophoretic techniques. A small amount of adult hemoblobin was constantly present, however, in hemolysates from fetuses older than 11 gestational wk, and it had the structural properties of adult hemoglobin A. Heterozygous fetuses had hemoglobins C and A or S and A as early as the 11th and 13th gestational wk. The findings are compatible with onset of beta hemoglobin gene action as early as the 11th gestational wk and synthesis of approximately 5% of adult hemoglobin by the end of the first and throughout the second trimester of gestation.

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The hemoglobins of fetal and adult Macaca nemestrina were investigated electrophoretically and chromatographically. Standard electrophoretic techniques failed to reveal variation in either fetal or adult hemoglobins beyond that previously attributed to the presence of the duplicate r-chain loci characteristic of this species. However, column chromatography of whole hemolysates on CM-Sephadex or of globin chains on CM-cellulose in 8 M urea revealed that some fetuses had four major hemoglobins and some adults had two major hemoglobin components. All animals examined were of Malaysian origin; the variation described is a consequence of variation in a-chain structure in Malaysian populations of this species, and of the interaction of different a chains with the products of the duplicate r-chain loci.

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