Speaking to experience in a statement of purpose for a PhD program. I am beginning the process of applying to PhD programs in Neuroscience for a fall 2015 start. I will be graduating this December with a Bachelor's in biology and math. I have been working as a research assistant for the last year, and our lab focuses on the role of extracellular matrix proteins in the col11a1-related chondrodysplasias. Although pursuit of a career in neuroscience research has been my goal, the biology program at my institution lacks faculty in this area; thus, my research experience is of questionable relevance to the programs I am applying for. 

I have three questions related to writing the statement of purpose:


I've heard that I am supposed to discuss my background in research. If my research isn't entirely relevant to neuroscience, should I restrict my discussion to the lab techniques I've learned, or can I speak in technical detail about my projects?
As mentioned, my current university lacks faculty who do research in neuroscience. Should I mention this as justification for my choice to work in my current lab, or should I omit it, as it may reflect poorly on my readiness for neuroscience?
I have a 3.85 GPA and my GRE scores were in the 93rd and 95th percentile (verbal and quantitative, respectively). To what degree will the statement of purpose affect my application, given the weaknesses addressed above?
I'm not sure that the statement of purpose is the right place to try to address deficiencies in your CV. Instead, let me suggest a different strategy. (I'll note in passing that I'm in Philosophy, in the USA--so take this with a grain of sand since you're in a different field. A second grain of sand if you are applying to programs in other countries.)

Use the Statement of Purpose to show the committee what you are going to do in the future, not to tell them why what you've done in the past isn't bad. 

Here's what I mean by the past/future comparison.

Bad: "I did a lot of work that is relevant, even though I know my CV didn't look like it." or "At my current lab job, I was taught techniques x, y, and z." Bad because it sounds like you are apologizing. It comes off weak, passive and submissive. You want to project confidence and competence, but not arrogance. Successful PhD students are people who are able to be self-motivated and don't have to have their hands held all the time.

Better: "I plan to apply my experience in techniques x and y, to problem z because . . . " This is better because it is active--it says what you are going to do rather than what has happened to you. 

The second distinction that is important is the distinction between showing and telling. 

Telling: "While working on this project, I acquired knowledge of techniques x, y, and z." This is weak because it just sounds like a list of things. There's no story--I don't get anything about your personality or your interests or what is special or unique about you as a candidate.
Showing: "We were interested in p, so I suggested we use technique x and we discovered r. A colleague who works in r suggested that we also apply technique y, which turned out to be the crucial step . . ." Now there's kind of a story that I care about a little bit. And I've learned more than just that you know x and y. I've learned that you know how to suggest techniques, and you're not afraid to tell the PI what you think, and that you know how to collaborate, etc. These are all good things. The committee gets a more complete, detailed idea of who you are as a candidate if you can show who you are and what you are interested in than if you just tell them. 

Most aspiring grad students (and newly minted PhDs!) are going to fall into the trap of telling rather than showing, so this is a good place for you to stick your neck out ahead of the pack.

Another example: Instead of using the SOP to say why you don't suck, use it to say why you want to go to this specific PhD program. Don't say, "I am interested in Neuroscience." That's telling. Instead: "I became particularly interested in question X after reading "X: an intriguing problem" by Prof Y." (where Y is somebody on faculty). You want to be specific about the strengths of each program.