DNA. We all know it as the building block of life, the very substance that makes us so similar and yet so different. The discovery of its double-helix structure 60 years ago on April 25, 1953, revolutionized the field of science and medicine.
DNA's existence was common knowledge by 1940. However, its status as the 'molecule of life' was highly disputed. Many people at that time thought that DNA was too simple to explain the vast diversity of life on our planet since it had only different amounts of the four bases (A,C,T,G). Proteins, with 20 amino acids, were favored over DNA as the molecule of life.
One of the properties of DNA is its ability to form crystals if treated in certain ways. Two scientists, Rosalind Franklin and Maurice Wilkins, used a technique called X-ray Crystallography to analyze the structure of the DNA crystal. Shining X-rays causes invisible rays to bounce off the crystal, which then creates complex patterns on photographic film.
Franklin, using X-ray Crystallography, took the infamous 'Photograph 51', which clearly showed the structure of DNA as a double helix. Here's where James Watson and Francis Crick come into the picture. Using Franklin's picture, they determined DNA's basic structure and then figured out base pairing (A-T, C-G). Their article in the journal Nature revolutionized science and earned them the Nobel Prize.
What Makes DNA Tick
First is its ability to remain intact for thousands of years, which allows us to date ancient organisms effectively. The structure of DNA is a bit like a 'twisted ladder' - The rails and rungs of this ladder are connected by chemical bonds whose collective strength requires a lot of energy to break. It is this "toughness" that has allowed biologists to study genes of ancient species.
DNA also provides the instructions that cells need in order to carry out their basic jobs. As the cells in our bodies grow, DNA can replicate easily and quickly. In DNA replication, the two strands separate, and each is used as a template strand to form another one. Think of it as making a new zipper, but using half of the old zip as a model.
From the four building blocks of DNA comes thousands of different proteins manufactured inside our body. Just one gram of DNA can hold about two petabytes of data - the equivalent of some 3 million CDs!
Today DNA is used is understand and cure inherited diseases, create genetically-engineered medicines such as insulin for diabetes, solve crimes, prove paternity in lawsuits, and create genetically modified foods. A newly emerging field based on this is 'DNA Computing', or the use of DNA to store artificially-produced information. The possibilities are endless!