Question

You have a small 4800 bp long circular DNA. It has a linking number of 450 (L=450). What are the twist (T) and the writhe (W) of this DNA? What assumptions about the structure of the DNA have you made in your answer? (Hint: what is the definition of the twist #?)

A) Twist (T) = 4800, Writhe (W) = 450; Assumes a linear DNA structure
B) Twist (T) = 450, Writhe (W) = 4800; Assumes a circular DNA structure
C) Twist (T) = 4350, Writhe (W) = 150; Assumes a relaxed, untwisted DNA structure
D) Twist (T) = 150, Writhe (W) = 4350; Assumes a highly supercoiled DNA structure

Answer 1

The twist (T) and the writhe (W) of a DNA molecule can be calculated based on its linking number. In the given scenario, the twist is 4800 and the writhe is 450, assuming a relaxed, untwisted DNA structure.

Step-by-step explanation:

The twist (T) and the writhe (W) of a DNA molecule can be calculated based on its linking number. The twist refers to the number of times the DNA helix crosses over itself, while the writhe refers to the number of times the helix is coiled upon itself. In the given scenario, where the DNA is a small 4800 bp long circular DNA with a linking number of 450, the correct values for twist (T) and writhe (W) would be Twist (T) = 4800 and Writhe (W) = 450. This assumes a relaxed, untwisted DNA structure (option C).