Our data agree with the hypothesis of a gene-nutrient interaction between MTHFR 677C-->T polymorphism and folate status that may confer a selective advantage of TT-homozygous genotype when dietary intake of folate is adequate, at least in the areas studied.

Background: A 776CRG variant (dbSNP ID: rs1801198) in the transcobalamin gene (TCN2; MIM# 275350) decreases the cellular and plasma concentration of transcobalamin and thereby influences the cellular availability of vitamin B 12 . Objective: To evaluate the worldwide prevalence of this variant and its association with homocysteine plasma level. Methods:The study was performed in 1433 apparently healthy subjects, including Afro-Americans and AfroAfricans and in 251 Afro-Africans participants with severe malaria. ) and in AfroAfrican patients with severe malaria (6.0%; 95% CI 3.7 to 9.6) than in healthy Afro-African volunteers (p = 0.0004 and p = 0.033, respectively), while no difference was observed for MTHFR 677TT and 677T alleles. A disequilibrium of TCN2 genotype distribution was recorded in patients with severe malaria, with a twofold higher GG genotype than expected (p = 0.010). An association between the TCN2 polymorphism and homocysteine was observed only in Mexico and France, the two countries with the highest rate of low plasma concentration of vitamin B 12 (,100 pmol/l). Conclusion: Given the dramatic heterogeneity of the 776G allele frequency worldwide, this polymorphism may be prone to a selective pressure or confers an evolutionary advantage in confronting environmental factors, one of which is malaria.

In the last article of our series, the Genetics Group, coordinated by Osvaldo Mutchinick, deals with the history of genetics and how future research will impact diagnosis and treatment of diseases

In the first of our new series about clinical genetics, Adrién J Gonzélez, Heidy R Arrieta, and Osvaldo M Mutchinick explain the fundamental principles of medical genetics, which provide the basis of prevention and treatment of genetic diseases