Final answer:
The additional coils formed when a double helix of DNA is twisted are known as supercoils, which are managed in cells by enzymes like topoisomerases.
Step-by-step explanation:
When a double helix of DNA is subject to twisting forces, it can form additional coils known as supercoils. Supercoiling occurs when the DNA helix is overwound or underwound, and it is a natural part of the DNA's structural organization. In living cells, enzymes such as topoisomerases are responsible for adding or removing twists in the DNA helix, which can relieve or introduce supercoiling, respectively.
DNA's structure as a double helix is the result of two strands of nucleotides that twist around each other, forming a shape resembling a spiral staircase. This configuration is stabilized by hydrogen bonds between the nitrogenous bases of the two strands, while the phosphate and sugar backbone forms the external structure. Under the influence of twisting forces, the DNA can become further twisted, and the additional coiling created is referred to as supercoiling.
Supercoiling is important for DNA function because it compactly the DNA molecule, allowing it to fit within the limited space of a cell nucleus and also plays a role in the regulation of gene expression and DNA replication.