Frequency and quantitative levels of T gamma chain (Hb F Sardinia) in the fetal hemoglobin of newborn and fetuses.
The fetal hemoglobin of 137 Dutch newborn has been examined by peptide mapping after digestion with trypsin, in order to detect the T gamma chain (gamma chain bearing a replacement Ile replaced by Thr at position 75) and to assess its quantity relative to the total gamma chains. Forty-two (31%) individuals were carriers of this variant, with an average amount of T gamma chain equal to 18.89% +/- 4.12 (1 SD). Three babies had T gamma levels higher than 30%, outside, therefore, the upper limit of the distribution. If we consider these three children homozygous carriers and assume that the remaining thirty-nine are heterozygotes, the gene frequency of T gamma in this population is 0.16 and the observed frequencies of the three phenotypes (T gamma-/-, T gamma+/- and T gamma +/+) agree closely with the expected ones. The occurrence and levels of T gamma chain are apparently not subject to variations during the last 25 weeks of gestation. In a group of twenty-nine fetuses investigated between the 12th and 20th week gestation, seven were, in fact, positive and showed T gamma percentages (12-26%) within the limits found in newborn. Also, the relative amounts of G gamma and A gamma chains were identical to those calculated in babies born at term. The composition of fetal hemoglobin remains, thus, uniform from the 12th week of gestation to birth. A comparison of the distribution of T gamma and A gamma percentages in T gamma positive newborn supports indirectly the identification of T gamma chain as a polymorphic variant of A gamma chain.
D005260:Female; D005312:Fetal Blood / Q000032:analysis; D005319:Fetal Hemoglobin / Q000032:analysis* / Q000235:genetics; D005333:Fetus; D005787:Gene Frequency; D006455:Hemoglobins, Abnormal / Q000032:analysis* / Q000235:genetics; D006801:Humans; D007231:Infant, Newborn; D046911:Macromolecular Substances; D010446:Peptide Fragments / Q000032:analysis; D010641:Phenotype; D011247:Pregnancy; D014357:Trypsin
D006455:Hemoglobins, Abnormal; D046911:Macromolecular Substances; D010446:Peptide Fragments; D005319:Fetal Hemoglobin; D014357:Trypsin