What do genetic test results look like?

A given SNP may occur in one or both copies of the gene. If found in only one copy, the patient is heterozygous (-/+) for the mutation. If the SNP occurs in both copies, the patient is homozygous (+/+) for the mutation (Figure 1).

Figure 1:

The three possible test results for every SNP. A homozygous genotype can have more significant health implications compared to the milder heterozygous genotype. For example, the C677T mutation in MTHFR reduces enzyme function by 70% and 35% in homozygous and heterozygous genotypes, respectively.