For simplicity one can think of the + class as having one extra base at some point or other in the genetic message and the - class as having one too few. ↗
I've been going through photos of my mother, looking back on her life and trying to put it into context. Very few people age gracefully enough to be photographed through their aging. ↗
I have just come from a couple of raids, where we had a very lively time, and some of them had to pull their guns. I found it necessary to punch a few sports myself. ↗