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DIYgenomics citizen science experiments - MTHFR mutations and Vitamin B12 deficiency

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A. Background

As a straightforward proof of concept for DIYgenomics citizen science, this study seeks to replicate and extend existing studies examining two possible mutations in the MTHFR gene, investigate the potential corresponding phenotype, Vitamin B12 deficiency, and in a later phase, determine if vitamin supplementation or other remedies may improve the deficiency.


B. Methodology/Principal Findings

Genotyping values will be sought from citizen science participants. Participants that are homozygous and perhaps heterogygous for the risk variants, will be asked to take a blood test to assess B12 deficiency. Questionnaires will also ask whether participants are or know if they are Vitamin B12 deficient. A period of vitamin supplementation will be


1. Gene mutation: MTHFR (Source: Wikipedia: MTHFR)


Methylenetetrahydrofolate reductase (MTHFR) is an enzyme that in humans is encoded by the MTHFR gene.


C677T SNP (Ala222Val)

The MTHFR nucleotide at position 677 in the gene has two possibilities: C or T. C at position 677 (leading to an alanine at amino acid 222) is the normal allele. The 677T allele (leading to a valine substitution at amino acid 222) encodes a thermolabile enzyme with reduced activity. Individuals with two copies of 677C (677CC) have the "normal" or "wildtype" genotype. 677TT individuals (homozygous) are said to have mild MTHFR deficiency. 677CT individuals (heterozygotes) are almost the same as normal individuals because the normal MTHFR can make up for the thermolabile MTHFR .


Population prevalence: About ten percent of the North American population are T-homozygous for this polymorphism. There is ethnic variability in the frequency of the T allele - frequency in Mediterranean/Hispanics > Caucasians > Africans/African-Americans). (Source: Wikipedia: MTHFR)


A1298C SNP (Glu429Ala)

At nucleotide 1298 of the MTHFR, there are two possibilities: A or C. 1298A (leading to a Glu at amino acid 429) is the most common while 1298C (leading to an Ala substitution at amino acid 429) is less common. 1298AA is the "normal" homozygous, 1298AC the heterozygous, and 1298CC the homozygous for the "variant". In studies of human recombinant MTHFR, the protein encoded by 1298C cannot be distinguished from 1298A in terms of activity, thermolability, FAD release, or the protective effect of 5-methyl-THF.[11] The C mutation does not appear to affect the MTHFR protein. It does not result in thermolabile MTHFR and does not appear to affect homocysteine levels.



Chr/Locus Gene
Genotype values Normal genotype(s)
Risk variant(s)
1p36.3 C677T rs1801133  
11778965 CT CC, CT TT
1p36.3 A1298C rs1801131 11777063 
AC AA, AC(?) AC(?), CC



1.a. DATA COLLECTION: participant genotyping data

Particpant rs1801133 rs1801131 Genotyping service Study group
Patient 0 AG GT 23andme-original edition Heterozygous/heterozygous


2. Phenotype: Vitamin B12 deficiency

Existing studies and other research



C. Conclusions/Significance






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