mthfr compound heterozygous = paternal + maternal alleles/mutations (from one or both parents)

https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=population+mthfr+gene+compound+heterozygous&*

Definition of Compound heterozygote - MedicineNet

www.medicinenet.com/script/main/art.asp?articlekey=33675

What does it mean to be a compound heterozygote?

Compound heterozygote: The presence of two different mutant alleles at a particular gene locus, one on each chromosome of a pair. The human genome contains two copies of each gene, a paternal and a maternal allele. A mutation affecting only one allele is called heterozygous.

Mutation - Wikipedia

https://en.wikipedia.org/wiki/Mutation

What is a heterozygous mutation?

A heterozygous mutation is a mutation of only one allele. A homozygous mutation is an identical mutation of both the paternal and maternal alleles. Compound heterozygous mutations or a genetic compound consists of two different mutations in the paternal and maternal alleles.