Mendel may be right, after all

I've been struggling with transgenic mice since after Christmas. I should have a 1 in 4 chance of getting my desired mouse, which will have a green fluorescent protein (GFP) in the cells I'm interested in. For those who this will mean anything to, I'm crossing a floxed stop GFP heterozygote with a het for my gene of interest driving cre. Right now, I can't use homozygotes to up my odds, for a variety of reasons. For those who the last two sentences were lost on, I need two different genes to be expressed at the same time to see green cells. Each gene has a 1 in 2 chance of being expressed and the genes are independently regulated, so the probability of having both is 1/4.

Anyway, the first 2 weeks I was 0 for 13 in being able to see GFP in my cells. I didn't believe it, my advisor didn't believe it, my collaborator who created the cre mouse didn't believe it - clearly, I was doing something wrong. Nope, PCR confirmed, I'm just that unlucky! (PCR is a way to amplify specific pieces of DNA. I'm using to see whether or not my genes are actually present in the DNA of each of my mice. As I said before, I need 2 genes to be present at the same time and not 1 of my 13 had both.) A guy in the lab next door overheard me talking to someone in my lab about my PCR results and he said that he was convinced that Mendel was wrong when he was starting his project. So, that became my explanation - Mendel was wrong.

This past week, my luck changed - 4 out of 8 of my mice had green cells! So, for those counting at home, that means I'm 4/21 overall, so far. You can't get much closer to 1/4 than that. So, I guess Mendel was right after all!