A recent study of the brains of elderly mice, for
instance, found 117 genes that were expressed
differently in the brains of animals that began a
program of running, compared with those that
remained sedentary
That's really interesting. I thought exercise just made me healthier now. I didn't know it actually might be altering my genes.
If this result applies to humans, then my exercising will also benefit my descendents!
This is correct, so it's not likely inherited (though we don't completely understand everything about inheritance such as the possible inheritance of miRNA). If you think of DNA as code, genes as specific programs, you can think of expression as how often those programs are run. "Running" in this sense means that the gene is copied to messenger RNA and send to the ribosome to synthesize proteins. Those proteins start as long chains like the dna/rna but immediately fold into complex shapes with unique properties that do various interesting things in the cell.
There was a scientific america article (I know not exactly "science") that showed how gene expression could in fact affect future offspring mainly through nurture. I believe the study was obese mice parents through gene expression would lead to obese mice children. However they believe this was caused through nurture.
Yes, those obese mice are called Agouti mice, and the concept overall is called epigenetics. The ON/OFF state of genes can be changed through diet, nurture, and more. For example, if you do not eat very nutritious food you might not have enough methyl groups to methylate (turn OFF) some of the genes that are currently ON but should naturally switch.
IANAB but I wouldn't be completely surprised if the gene expression of an egg or sperm cell or fetus depended on the conditions of the parent. (I wouldn't be surprised otherwise, if sperm and egg cells are designed to be as independent as possible from the parent.) It might not be gene expression in particular, after all, drug use affects babies, so why not obesity? Of course we were originally talking about gene expression within brains.
If this result applies to humans, then my exercising will also benefit my descendents!