DNA is the abbreviation of deoxyribonucleic acid. It is a very complex molecule, residing in the nucleus of every cell of an organism, except a few exceptions. For all living beings, DNA is a tool for storing their genetic code, which is similar for every organism. For example, you have well over 95% of the same DNA as a chimpanzee.

To know more about DNA and how it works, we first need to know about amino acids, so here is a brief description:

Amino acids are very important little chemicals that are present in the cytoplasm of a cell. They come in about twenty different kinds, and combine with each other to form proteins, millions of different types of them. The proteins in turn, form living cells, which form tissues, which form organs that, when put together properly, form an organism,

The main function of DNA is to ensure correct formation of proteins from amino acids, as even a minute mistake leads to malfunctioning of the protein.

Shown above is an overly simplified model of DNA.

As you can see, DNA is shaped like a ladder, which in reality is twisted into a double helix. The steps of the ladder are made of four different kinds of chemicals, known as nucleotides, which are denoted by colour and letters. They are:

· Thymine --- T

· Adenine --- A

· Cytosine --- C

· Guanine --- G

DNA is locked inside the nucleus of the cell, inside chromosomes, while amino acids are present outside, in the nucleus. So, it needs a way to get the genetic code out of the nucleus, without breaking it. To do this, DNA produces RNA or ribonucleic acid.

RNA can be defined as a copy of one side of a part of DNA. Due to its small size, RNA can fit through tiny pores on the wall of the nucleus, and get out of it. The nucleotide Uracil (U) replaces thymine in RNA.

Outside the nucleus, RNA makes its way to another part of a cell, ribosomes. Observe in Fig.1 that the nucleotides only form bonds with specific other nucleotides. For example, adenine and thymine only make bonds with each other, and guanine and cytosine as well. Therefore, if you know the first half of the genetic code, you can decode the other half.

Since RNA is only half the gene code required, ribosomes use this property to construct the other half as well, so RNA is used as the required DNA outside the nucleus.

Ribosomes are protein-building factories, which are able to align, connect and shape amino acids into the required type of protein. They have the tools to do that, but not the information on which proteins to make, or how to make them. This is where DNA comes in. DNA tells the ribosome exactly how much of which protein to make, and precisely how to make it.