Answer:
The number of complete rotations in a DNA molecule is related to its structure and length. In this case, the DNA molecule is 300 base pairs (bp) long and has 20 complete rotations. Based on this information, we can conclude that this DNA molecule is a supercoiled circular DNA molecule.
Circular DNA molecules can become supercoiled when the strands of the double helix twist around each other. This twisting can result in overwinding or underwinding of the DNA, leading to the formation of supercoils. In the case of this 300 bp long DNA molecule, the 20 complete rotations indicate that it has a high degree of supercoiling.
Therefore, the DNA molecule that is 300 bp long and has 20 complete rotations is a supercoiled circular DNA molecule.
Step-by-step explanation: