Variance is always non-negative since each term in the variance sum is squared and therefore the result is either positive or zero.

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#Unit 2. Cellular Organization

The second level of organization is the coiling of the 10-nm fiber of nucleosomes into a helical array to constitute the fiber of diameter 30 nm.

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#Unit 2. Cellular Organization

30 nm compacts the DNA 40-fold. This structure of this fiber requires the histone tails and is stabilized by linker histones.

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#Unit 2. Cellular Organization

This 30-nm fiber is further folded, results in 1000-fold compaction in euchromatin in interphase chromatin and in mitotic chromosomes to achieve an overall 10,000- fold compaction in euchromatin.

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#Unit 2. Cellular Organization

Heterochromatin generally maintains 10,000-fold compaction in both interphase and mitosis after 30 nm.

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#Unit 2. Cellular Organization

Chromatin contains DNA, Histones, Nonhistone Proteins and RNA. RNA polymerase is a prominent nonhistone protein

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#Id: 428

#Unit 2. Cellular Organization

Individual nucleosomes can be obtained by treating chromatin with the endonuclease micrococcal nuclease (MNase), which cuts the DNA between nucleosomes, a region known as linker DNA.