# The Nucleosome

On the previous page, you have seen the complete structure of the nucleosome - but what are its constituent parts? Have a look at the next structure, you will notice that the core of the nucleosome consists of several similar porteins.

How many proteins make up the histone core of the nucleosome? The correct answer is:

The correct answer is: The core consists of 8 histones.
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The histones are organised in a pairwise manner, i.e. each two histones build a so-called dimer. Their orientation in this dimer structure reminds of two people shaking hands (hence, this structural motif is called a "handshake motif"). The two histones build a firm, interleaved unit that is the basis of the nucleosome. The histone core is constructed like a puzzle; in the first step, a tetramer is deposited onto the DNA.

Can you identify what exactly a tetramer is and how each two histones interact forming the handshake motif? The correct answer:

The correct answer: A tetramer consists of 4 histones.
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The tetramer is flanked by 2 dimers in the subsequent step and thus complete the histone core and the nucleosome, respectively.

Can you identify the constituent parts (DNA and 8 histones) of the complete nucleosome in the following structure?