This came as a bit of a surprise to me. I was taught early on that we each inherited two sets of genes, one from our mother and one from our father in the form of DNA. These inherited genes were then responsible for all of our genetically governed traits. This article in the Economist (subscription required) suggests that
genetic information comes from places other than inherited DNA.
Based on studies of a gene called Kit French researches believe they have found that in some cases RNA can be passed from parent to child... but in this case RNA that has no relation to the DNA passed from that parent. In this manner, offspring may end up with RNA, and thereby DNA from a parent or grandparent, but lack the DNA that would have been expected to code for that RNA. The article states:
When this RNA was extracted and injected into mice embryos, a white-tailed mutant was created—even though no genes for the white tail were present. This work shows that the inheritance is mediated by RNA but the precise mechanism is unclear. The inherited RNA could be interfering with messages sent by the inherited DNA, or it could be directly modifying inherited DNA.
The phenomenon observed has been coined paramutation and is believe to be able to persist across generations, and has been grouped as an 'epigenetic' effect - defined in the article as
hereditary changes in gene function put down to chemical changes rather than the sequence of DNA.
From The Economist