Im just not quite sure the answer to this. When we talk about epigenetics and gene expression, does it not matter if we have snp's or not
I think
@Jonathan Edwards explained expression pretty well. It's not really like you have some dormant freakish mutation which suddenly comes to life and tries to eat you. It's more of a tweaking in regulation which happens outside of the strictly genetic aspect.
For instance, if you have +/- then you could be expressing either the mutation or correct gene because you have both options.
That wouldn't really be about expressing, but about the SNPs themselves. If the SNP has been studied, then the size of the impact is usually known. +/- doesn't mean a 50/50 chance of it working or not, but rather how that SNP impacts gene functioning. On some genes, +/- for a SNP means that the gene functions at or near 100%, even if being +/+ means a drastic alteration in gene functioning. On other genes, a +/- SNP can be enough to cause a disease, or cause a big alteration in gene functioning - it depends on the gene and the way it operates.
A good example is MTRR versus MTHFR. To have a big reduction in MTRR functionality, it has to be +/+ for a SNP, or compound heterozygous (one from each parent) on two missense mutations which are capable of causing problems. But for MTHFR, being +/- on an important missense mutations will have a big impact, albeit less of an impact than being +/+. This is quite consistent for all of the missense mutations I've seen research for on those genes. They each have a different rule, but follow their own rule very consistently.
If you're +/+, or contrary, -/- does gene expression even matter since both copies of your genes are the same so you can't really "express" something different?
If someone is talking about gene expression on the internet (blog, forum, etc) as being an explanation for yours (or others) specific genetic results, they're usually just talking out of their rectum. Basically they have invested in making ridiculous claims about specific SNPs which are based on Yasko's bizarre claims, which are usually contradicted by the research when there is any. They cannot deny that those claims about the SNPs are wrong, so now they invent vague and completely unsubstantiated claims regarding "expression" of genes. Apparently they expect these SNPs to behave in a radically different manner when some mythical trigger comes along, despite the complete lack of scientific support for these claims.
If someone's talking about "genetic expression" in that context, it's a good sign that they're a quack, or a wannabe quack.