If chromosomes are masses of DNA circles all stuck together, what does the sticking?

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:

Fig11

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.

Fig12

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:

rubber band fused circles

Fig19Fig20

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.

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About frankabernathy

I am a retired cell biologist and alumnus of Ohio State University. I became interested in chromosomes as far back as the 1960's when I wrote a term paper on the effects of radiomimetic drugs on chromosomes. I was fascinated at how they could break apart and reform new structures so easily. I became further involved in the early 1970's after taking a cytogenetics course at the University of Arkansas. I took that knowledge with me to Ohio State in 1980 where I eventually worked on my research and completed my Ph.D. dissertation, "Studies on Eukaryotic DNA Superstructure". My studies and later research suggested that the DNA within the eukaryotic chromosome is not the simple, linear molecular thread so widely suggested in all the classic textbooks published today. Instead, it may be the culmination of a geologically rapid set of endosymbiotic events where microorganisms plug into each other to create something greater than themselves. Feel free to contact me at fabernathy@sbcglobal.net.
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