What Is DNA?

Deoxyribonucleic acid, more commonly known as DNA, is the molecule that contains genetic information of an individual. Each one of us has our own DNA fingerprint, genetic information that is unique to only us. Only identical twins share genetic information.

A German biochemist called Frederich Miescher was the first to observe DNA back in 1869. It wasn’t until 1953 however, that three other scientists figured out its structure and its role in carrying genetic information. They went ahead to win the Nobel Prize in Medicine in 1962 for their discovery.

The genetic information that is found in DNA acts like an instruction manual for how an individual is going to develop, live and ultimately reproduce. Nucleotides are the molecules found in DNA, and they attach themselves to each other to form two very long strands that twist and form a double-helix shape. The nucleotides contain a phosphate, a sugar and a nitrogen base. There are four types of nitrogen bases- adenine, guanine, thymine and cytosine. These bases act as building blocks, and their arrangement is what ultimately forms the instruction manual of somebody’s genetic information, i.e genes.

The double helix shape of DNA can also be described as a twisted ladder, where the phosphate and sugar molecules of the nucleotides form the sides of the ladder, and the nitrogen bases form the rungs. These bases always pair in the same way, where the adenine on one strand will always pair with the thymine, and the guanine will always pair with the cytosine. The pairs are joined by hydrogen bonds.

DNA molecules are usually very long, and if one was to be stretched out, it would be about two meters long. This whole length has to fit into each cell, and it is for this reason that DNA is packaged and coiled tightly to form a cell structure known as a chromosome. One chromosome contains a single DNA molecule, and human beings have 23 pairs, which can be found in the cell nucleus.

22 pairs of chromosomes are what usually contain most of the hereditary genetic information, and they are known as autosomes. The remaining pair is what determines the gender of a child, and it’s known as the sex chromosome. It can be either X or Y. Females have two X chromosomes, and they can pass only this to their child. Males have the X and Y chromosomes, and it is in fact their chromosomes that determine what gender the child will be. If they pass on the X chromosome to the child, it will be female. If the Y chromosome is what is passed down, the child will be male.

One very important trait of DNA is its ability to replicate during cell division. This ensures that during cell formation, the new cells have the same copy of DNA as the old cells. Recently, scientists have developed a technology known as DNA sequencing, which allows them to figure out which parts in DNA carry hereditary genes, and which ones carry the instructions that can turn the genes on or off. This is what has been a major part of DNA testing for health, among other things.

  • Updated September 9, 2017
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