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.
Dr. Ben Lynch, who is considered one of the foremost experts in the field of MTHFR genetic mutations, has a more complete list here. (See the third paragraph for a link to additional supporting research.) Are all MTHFR mutations the same? No. There are over fifty types of MTHFR gene mutations . . . possibly more that have yet to be discovered. However, the two that are most commonly studied and tested for are C677T and A1298C. Letâs look at the C677T mutation for a moment.