This entire blog has been about throwing out old textbook models of simple linear chromosomes and replacing them with a model of circular DNA’s all stuck together to generate a huge complex mass. This allows the genes to communicate with one another in a more streamlined way with regards to cellular differentiation and gene expression. Such a hypothesis demand models for how this might happen.
Here they are:
In this model, circular DNA’s bind to one another at their origins of replication using 2′ RNA bonds, creating a covalent tetrahelical complex.
Evidence for 2’5′ RNA bonds abound in the literature, especially with regards to intron lariat loops. However, they also appear to be involved in some kinds of viral DNA replication as well. Another interesting alternative would be the role (if any) of DNA phosphotriester bonds in this hypothetical process. For now, however, the emphasis here will be on the 2′ model.
This model shows how such a 2′ RNA structure could be used to bind two origins of replication together and how they could be fused together under certain conditions.
The result is the rubber band model shown in the next to the last blog:
The model on the left illustrates how a promoter could be generated from a double origin of replication during the course of cellular differentiation. The one on the right illustrates how a splice site could be generated either from a double origin or possibly a promoter. An enhancer site (not shown here) would be the result of the two circles of DNA completely separating from one another.
Questions and comments are always welcomed. In the next blog, I will put up a model for how an entire chromosome might be constructed using this method.