A quick answer to your question #1/2: microRNA (miRNA) is the substrate of a very complex piece of cell machinery that uses the miRNA sequence to find complemen

A quick answer to your question #1/2: microRNA (miRNA) is the substrate of a very complex piece of cell machinery that uses the miRNA sequence to find complementary messenger RNA (mRNA). When miRNA binds to its respective mRNA, the machinery (whose details I will not go into) degrades the mRNA, preventing its translation into protein. So while the DNA remains unaltered by the miRNA, protein expression is regulated on the level of mRNA degradation. MiRNA and short-hairpin RNA are tremendously useful in the laboratory setting to knock down the expression of genes without having to do gene modifications. This paper shows that miRNA can be passed from father to child through the sperm, and this miRNA can affect the way certain genes are expressed. As for your question #3, I couldn't find any information in the paper regarding how long the miRNA persisted in the offspring. The miRNAs seem to have a long-term effect on genes in the paraventricular nucleus of the hypothalamus, but whether this is due to effects of miRNA solely in the development of the zygote, or whether the miRNA in the adult is also important, is unclear. It seems likely that changes due to the miRNA in fetal development alone could be sufficient in dramatically changing stress responsitivity, but this remains to be proven. In another famous study, maternal nurture plays a very important role in the epigenetic development of baby mice [1]. So it could very well be that a favorable and nurturing environment may cause epigenetic changes in the offspring that might counteract the actions of the miRNA described here. Again, this is something that the paper does not show and therefore we can only speculate at this point. Hope this helps! [1] http://www.nature.com/neuro/journal/v7/n8/full/nn1276.html http://www.nature.com/neuro/journal/v7/n8/full/nn1276.html