Section 15 — Human Genetics 



15.81. Variable Heterozygote Expression in Human 

 Haptoglobins. H. E. Sutton and G. W. Karp 

 (Austin, U.S.A.). 



Two alleles are commonly recognized at the 

 human haptoglobin locus, Hp l and Up 2 . In 

 most populations, the heterozygous phenotypes 

 are very similar. However, in Negro populations 

 a variant, Hp 2-1 modified, has been described. 



Our studies of an American Negro population 

 indicate that a broad range of heterozygous 

 phenotypes are found, depending on the relative 

 activity of the two alleles. The limited evidence 

 suggests that the differences in allelic activity 

 are not the result of structural differences of the 

 products. Studies of more than 100 matings of 

 various types show that in some families there 

 are factors which influence the activity of the 

 alleles differentially. Ahaptoglobinemia tends 

 to occur in the same families. 



Analysis of the mating studies will be presented 

 and the haptoglobin system will be discussed 

 from the viewpoint of newer ideas on gene regu- 

 lation. 



of the gestation period and of those from the 

 fathers and from normal controls, are also re- 

 ported and discussed. 



15.82. Possible Influence of Mother's Genotype on 

 the Foetal Haptoglobin Synthesis. M. Sinis- 

 calco, G. La Torretta, C. Del Bianco, 

 S. Marsico and L. Bernini (Naples, Italy). 



The incidence of cordal blood plasma with a 

 detectable haptoglobin pattern has been found to 

 vary considerably in the different haptoglobin 

 types of mating, suggesting the possible in- 

 fluence of the mother's genotype on the foetal 

 haptoglobin synthesis. 



Thus the lowest incidence (4.3 per cent) was 

 found among the "incompatible matings" i.e. 

 when the baby must necessarily possess a 

 molecular haptoglobin species not produced 

 by the mother, and the maximum incidence 

 (23.8 per cent) among the full compatible mat- 

 ings, i.e. those involving a 2.1 mother or parents 

 with identical haptoglobin genotype. 



Passive transfer of haptoglobin from the ma- 

 ternal to the foetal circulation is excluded on the 

 ground that the detectability of haptoglobin at 

 birth is not positively correlated with the 

 haptoglobin concentration of maternal plasma 

 and also because of the frequent occurrence of 

 cord blood plasma with a haptoglobin pattern 

 unlike that of the mother. 



Extensive data on the quantitative hapto- 

 globin levels of the cordal blood plasma with 

 or without detectable haptoglobin pattern, of 

 the blood plasma from the mothers at the end 



To be published in full in: Acta Genetica et 

 Statistica Medica, Karger, Basel. 



15.83. Asynchrony in the Synthesis of the Polypep- 

 tide Chain and Carbohydrate Prosthetic Groups 

 in Human Transferrin. W. Carey Parker and 

 Alexander G. Bearn (New York City, 

 U.S.A.). 



Transferrin C, the specific iron-binding com- 

 ponent of human serum, is a glycoprotein of 

 molecular weight approximately 90,000 whose 

 carbohydrate moiety contains glucose, man- 

 nose, glucosamine, fucose, and sialic acid. 

 Recent studies on several glycoproteins by 

 various authors have demonstrated the occurence 

 of prosthetic groups of multiple carbohydrate 

 residues attached at various points to the 

 polypeptide chain of the protein; sugar nu- 

 cleotides have also been isolated which contain 

 similar carbohydrate groups. Stepwise removal 

 of the four sialic acid residues of transferrin can 

 be accomplished by the enzyme neuraminidase; 

 transferrin devoid of sialic acid retains the iron- 

 binding, antigenic, and sedimentation properties 

 of untreated transferrin. Purification and ana- 

 lysis of a primate transferrin reveals that it 

 contains half the human complement of both 

 sialic acid and glucosamine. Cord serum from 

 newborn infants contains, in addition to trans- 

 ferrin C, four additional iron-binding compo- 

 nents which migrate slightly more rapidly by 

 starch gel electrophoresis than the correspond- 

 ing components in the pattern of neuraminidase- 

 treated adult transferrin. The faint components 

 disappear within 6-12 weeks of birth. These 

 observations suggest that the differences in 

 mobility result from alterations in the molecule 

 in addition to the absence of sialic acid and are 

 consistent with the interpretation that a mecha- 

 nism responsible for the addition of carbohy- 

 drate prosthetic units (containing glucosamine 

 and sialic acid) functions imperfectly at birth, 

 so that not all of the transferrin molecules 

 receive the full complement of sialic acid- 

 containing prosthetic groups. A similar pheno- 

 menon is present in human cerebrospinal 

 fluid, where two principal populations of trans- 

 ferrin molecules appear to exist, one with the 

 full complement of sialic acid-containing pros- 

 thetic groups, the other devoid of such groups. 



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