∞ generated and posted on 2016.08.28 ∞

Description of the DNA within the nucleus of eukaryotic cells along with DNA-associated proteins.

Qualifying "nucleus" with "eukaryotic cells" of course is redundant since all eukaryotic cells have one or more nuclei and all cells with nuclei (more or less) are eukaryotic. Nevertheless, the point is to include "eukaryotic" while at the same time excluding cytoplasmic DNA such as that found in mitochondria and chloroplasts, which is much less complex in its structure than nuclear DNA. Chromatin itself can be distinguished into euchromatin versus heterochromatin.

Another qualification is that chromatin is not identical to the DNA found in metaphase chromosomes since the latter is much more compact and, indeed, possess additional proteins and associations than the interphase chromatin. Thus, we can distinguish eukaryotic nuclear DNA into at least two different structures, that seen during interphase of the cell cycle, which is less compact and known as chromatin, and that that seen during metaphase, which is much more compact and known as chromosomes.

Further distinctions include that chromatin is not nearly as easily visualized using a light microscope than are chromosomes, that chromatin is associated with gene expression whereas chromosomes are somewhat resistant to being transcribed, and that it is during prophase of mitosis that chromatin is converted into chromosomes whereas it is during telophase that chromosomes are converted into chromatin. It is also worth noting that the term "chromosome" is often used somewhat ambiguously, that is, many people describe and often even draw in diagrams chromatin as chromosomes!

An additional issue is that it is not as though prokaryotic DNA is devoid of association with proteins. Indeed, the histones, which are key protein components of chromatin, while not associated with the DNA of members of domain Bacteria, nonetheless are associated with the DNA of at least some members of domain domain Archaea.