In 2005, about 20 percent (82,600 million gallons per day (Mgal/d)) of total national water withdrawals (about 410,000 Mgal/d) came from groundwater sources. (All 2010 water use information is from the report Estimated use of water in the United States in 2010.) Very little saline groundwater was used in 2005.
The MTHFR nucleotide at position 677 in the gene has two possibilities: C (cytosine) or T (thymine). 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.
The MTHFR Gene. There are currently a total of 34 mutations in the MTHFR gene. The MTHFR gene sits on Chromosome 1. There are two key variants we test for (as at this stage there is little or no research on the others). SNPs that we currently test for: MTHFR C677T; MTHFR A1298C; Heterozygous = 1 copy of the gene from either parent Homozygous = 1 copy of the gene from each parent. MTHFR C677T Heterozygous = 40% loss of function * MTHFR C677T Homozygous = 70% loss of function * MTHFR A1298C Heterozygous = 20% loss of function (research not known) MTHFR A1298C Homozygous = 40% loss of function **