homozygous a1298c mutation
Of these, MTHFR C677T and A1298C mutations are among the most common. If a person has two copies (homozygous) of MTHFR C677T, or has one copy of C677T and one of A1298C, then it is likely that elevated homocysteine levels are due to these inherited mutations, or that the mutations are contributing to them.wo copies of A1298C are not typically associated with increased homocysteine levels. If the MTHFR mutation test is negative, then the C677T and A1298C mutations were not detected and the tested person's elevated homocysteine level is likely due to another cause.