Chargaff’s Second Parity Rule

Abstract

Information has many forms. If you turn down the corner of a page to remind you where you stopped reading, then you have left a message on the page (‘bookmark’). In future you ‘decode’ (extract information from) the bookmark with the knowledge that it means “continue here.” A future historian might be interested in where you paused in your reading. Going through the book, he/she would notice creases suggesting that a flap had been turned down. Making assumptions about the code you were using, a feasible map of the book could then be made with your pause sites. It might be discovered that you paused at particular sites – say at the ends of chapters. In this case pauses would be correlated with the distribution of the book’s ‘primary information.’ Or perhaps there was a random element to your pausing – perhaps when your partner wanted the light out. In this case pausing would be influenced by your pairing relationship. While humans not infrequently get in a flap about their pairing relationships, we shall see that flaps are useful metaphors when we observe DNA molecules in a flap about their pairing relationships.