What is the structure of chromatin?
This is a question that has stumped scientists for more than 30 years, and two alternative models exist to explain chromatin's internal structure, and how the nucleosomes are arranged.
First of all a definition - nucleosomes are the fundamental units of chromatin and consist of tightly coiled DNA around a histone protein spool.
The two chromatin models:-
1) A solenoid formation - here the nucleosomes follow a helical path so that adjacent nucleosomes lie side by side
2) A zigzag formation - here, according to some researchers, the nucleosomes follow a zigzag path along the chromatin fibre so that adjacent nucleosomes are opposite each other.
In August 2009 scientists from UC San Diego Jacobs School of Engineering, Penn State University, University of Massachusetts, and New York University came up with a third model, and it consists of both the solenoid and the zigzag formation that are in balance with each other and present at different times - a heteromorphic structure.