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Essential Cell Biology 5th edition

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198 CHAPTER 5 DNA and Chromosomes

QUESTION 5–16

A single nucleosome core particle is 11 nm in diameter

and contains 147 base pairs (bp) of DNA (the DNA double

helix measures 0.34 nm/bp). What packing ratio (ratio of

DNA length to nucleosome diameter) has been achieved by

wrapping DNA around the histone octamer? Assuming that

there are an additional 54 bp of extended DNA in the linker

between nucleosomes, how condensed is “beads-on-astring”

DNA relative to fully extended DNA? What fraction

of the 10,000-fold condensation that occurs at mitosis does

this first level of packing represent?

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