Question

A chromatin fiber of 40 nm length contains 25 nucleosomes (200 bp per nucleosome). The degree of compaction of DNA associated with this chromatin fiber is .............. fold (decimal digits up to 1 place)

Hint:

To calculate the degree of compaction of chromatin, divide the total length of DNA by the length of the chromatin fiber.

Answer 1

Correct Answer: 42.1

Step 1: Calculate the total length of the DNA.
Each nucleosome contains 200 base pairs, and there are 25 nucleosomes in the chromatin fiber. The total length of DNA in the fiber is: \[ \text{Total DNA length} = 25 \times 200 \, \text{bp} = 5000 \, \text{bp}. \] Since each base pair is approximately 0.34 nm long, the total length of DNA in nm is: \[ \text{Total DNA length in nm} = 5000 \times 0.34 = 1700 \, \text{nm}. \]

Step 2: Compare the DNA length with the chromatin fiber length.
The length of the chromatin fiber is 40 nm, so the degree of compaction is: \[ \text{Degree of compaction} = \frac{\text{Total DNA length in nm}}{\text{Chromatin fiber length in nm}} = \frac{1700}{40} = 42.5. \]

Step 3: Conclusion.
The degree of compaction of DNA associated with this chromatin fiber is approximately 8000 fold.