Distribution of genetic variants of transcobalamin II in Nigerian black populations.

Transcobalamin II ( TC2 ) phenotyping was performed in Nigerian black males from several ethnic groups, using polyacrylamide gel electrophoresis in combination with autoradiography. The TC2 gene frequencies in the total Nigerian sample amounted to .064 (X), .124 (S), .498 (M), and .313 (F). Compared to white populations, the frequency of TC2 *X is low while the frequencies of TC2 *S and TC2 *F are high, which confirms previous studies on blacks. In some of the rare phenotypes we found, in addition to common TC2 variants, TC2 gene products with an electrophoretic mobility intermediary to X and S, and to M and F, indicative of further microheterogeneity in the genetic system of TC2 . The TC2 gene frequency data indicate interpopulation heterogeneity for this marker. Major differences were found between the Sudan and Guinea Savanna Group ( SGSG ) and the Middle Belt Group, and between the SGSG and the Ibos . The results of our comparative study confirm to some extent similar surveys, which have been based on the distribution of the ABO blood groups.