This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Metabolism of nucleic acids, Subject name: Biochemistry
What is the role of H2 histone? 
Select and explain. 
A. Stabilize the 30-nm chromatin fiber, B. Central role in the formation of the nucleosome, C. Stabilizes the primary paicle, D. Firmly binds two additional half-turns of DNA
D: Firmly binds two additional half-turns of DNA
Answer: D: Firmly binds two additional half-turns of DNA 
Explanation: Types Function H1 histones Stabilize the 30-nm chromatin fiber H2 histones H2A-H2B dimers stabilize the primary paicle and firmly bind two additional half-turns of DNA H3 histones H4 histones (H3-H4)2 tetramer has a central role in the formation of the nucleosome Reference: Harpers illustrated biochemistry 30th edition