What Is DNA?

Deoxyribonucleic acid (DNA) is a nucleic acid present in the cells of all living organisms. It is often referred to as the “building blocks of life,” since it encodes the genetic material that determines what an organism will develop into. In addition to maintaining the genetic blueprints for its parent organism, DNA also performs a number of other functions which are critical to life.

This nucleic acid was first identified in 1889, when researcher Friedrich Miescher found a substance he called “nuclein” in human cells. In the early 20th century, several researchers, including Phoebus Levene and William Astbury, performed additional research on nuclein, beginning to understand its components, structure, and role in life. A seminal article published in Nature in 1953 by James Watson and Franklin Crick is often cited as the breakthrough moment, as it correctly posited the distinct structure of this acid, with significant help from scientist Rosalind Franklin.

DNA is composed of chains of nucleotides built on a sugar and phosphate backbone and wrapped around each other in the form of a double helix. The backbone supports four bases: guanine, cytosine, adenine, and thymine. Guanine and cytosine are complementary, always appearing opposite each other on the helix, as are adenine and thymine. This is critical in the reproduction of the genetic material, as it allows a strand to divide and copy itself, since it only needs half of the material in the helix to duplicate successfully.

This nucleic acid is capable of self replication, and it also contains the code necessary for synthesizing RNA, another critical nucleic acid. It contains sets of base pairs that come together to create the genetic code, determining things like eye color and body structure. Each cell in the body contains DNA that is more or less identical, with more being produced all the time as cells replicate themselves. The vast majority in most organisms is non-coding, meaning that it does not appear to have any known function.

When DNA becomes altered by a substance known as a mutagen, it can cause health problems. Some mutagens have an impact on DNA in the eggs and sperm, or on developing organisms, causing them to develop birth defects. Others can change living organisms, contributing to the development of a variety of health problems. Mutagens often introduce errors at the copying stage, which means that these errors will be replicated numerous times as the damaged material perpetuates itself.