Wrapping double-helical DNA around histone octamers condenses the DNA by a factor of 7. Higher order...

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Chemistry

Wrapping double-helical DNA around histone octamers condensesthe DNA by a factor of 7. Higher order chromatin structurescondense this DNA even further. During metaphase, the DNA iscompacted by a factor of 1 Ã— 10⁴. How many centimeterswould the naked double-helical DNA from a 50 Mb chromosome stretch?(Note: Assume the DNA remains in the B-form, which has arise per base pair of 0.34 nm.)
A. 0.017cm
B. 0.17 cm
C. 0.68 cm
D. 1.7 cm
E. 6.8 cm

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3.9 Ratings (730 Votes)

Correct option A: 0.017 cm

Length of fully extended (naked) 50 Mb chromosome stretch = 50 x10⁶ bases x 0.34 nm

Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â = 17.0 x 10⁶ nmÂ Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â [1nm = 10^-9 m]

Â Â Â Â Â Â Â Â Â = 1.7 x 10^-2 m = 0.017 cm Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â [1 m = 100 cm]

Rise per base pair means the vertical distance (elevation) between two adjacent bases as they rise along the helix. It gives the length of the naked DNA itself.

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