Take a look at your hands side by side. Now place them on top of each other. Although the same, you cannot align them. When you place them side by side you realise that they are mirror images of each other. This is because your hands are an example of chirality, the Greek word for hands, where an object is distinguishable from its mirror image.
Chirality can be seen in the natural world but one of the most interesting and perplexing examples of chirality is DNA.
The two strands of DNA twist into a helix to form the well-known double helix structure, but the question is why is it chiral? Why is the chirality of DNA necessary?
The compaction of DNA is necessary to bring sections of DNA closer together and allow direct contact between helices. It is also a means of fitting DNA inside the cell. It has been proposed that this strengthens the effect of the chirality, and that the chirality of the helix structure avoids repulsion between the helices due to the charge of DNA.
It has also been found that the very molecules that make DNA are also chiral, so others speculate that there is no reason for chirality but that it has always existed and nature has adapted to this phenomenon.
Heilbronner, Edgar, and Jack D. Dunitz. Reflections on Symmetry: In Chemistry–and Elsewhere. John Wiley & Sons, 1993.
Int. J. Mol. Sci. 2013, 14(4), 8252-8270; doi:10.3390/ijms14048252