{{Rsnum
|rsid=1802059
|Gene=MTRR
|Chromosome=5
|position=7897206
|Orientation=plus
|GMAF=0.2489
|geno1=(A;A)
|geno2=(A;G)
|geno3=(G;G)
|Gene_s=MTRR
|Assembly=GRCh38
|GenomeBuild=38.1
|dbSNPBuild=141
}}{{ population diversity
| geno1=(A;A)
| geno2=(A;G)
| geno3=(G;G)
| CEU | 9.1 | 43.6 | 47.3
| HCB | 2.3 | 23.7 | 74.0
| JPT | 0.9 | 13.6 | 85.5
| YRI | 3.4 | 40.0 | 56.6
| ASW | 5.7 | 52.8 | 41.5
| CHB | 2.3 | 23.7 | 74.0
| CHD | 2.8 | 26.9 | 70.4
| GIH | 15.0 | 45.0 | 40.0
| LWK | 11.2 | 43.9 | 44.9
| MEX | 3.4 | 31.0 | 65.5
| MKK | 20.0 | 51.0 | 29.0
| TSI | 11.8 | 50.0 | 38.2
| HapMapRevision=28
}}[[Yasko Methylation]] Methionine synthase, coded by the MTR gene, has a B12 attached to it. The Methionine synthase takes a methyl group from methyl folate and attaches it to its B12, then it attaches it to a molecule of homocysteine, turning it into methionine, which in turn becomes SAMe. After 1000-2000 times doing this, the B12 gets turned into a useless form, and MTRR turns the B12 back into the useful form so that the molecule of MTR can keep working. The MTRR mutations make this enzyme less active, suggesting a need for more B12.

{{PMID Auto
|PMID=19493349
|Title=118 SNPs of folate-related genes and risks of spina bifida and conotruncal heart defects.
|OA=1
}}

{{PMID Auto
|PMID=20445798
|Title=Chromosome 5p Region SNPs Are Associated with Risk of NSCLC among Women.
|OA=1
}}

{{on chip | 23andMe v1}}
{{on chip | 23andMe v2}}
{{on chip | 23andMe v3}}
{{on chip | 23andMe v4}}
{{on chip | FTDNA2}}
{{on chip | HumanOmni1Quad}}
{{on chip | Illumina Human 1M}}