(RNA = abbreviation for Ribonucleic acid)

Messenger RNA (mRNA) is the “transcript” of a gene. It contains the blueprint for the production of a protein.

Why do genes have to be transcribed first in order for proteins to be generated according to their instructions?

The genes are contained in very long DNA strands. If we were to unwind and link the 46 DNA strands of one cell, they would measure almost two meters in length. However, the cell nucleus is two hundred times smaller than a pinhead. While the DNA strands fit into the cell nucleus when well wound and folded, they do not fit through the small channels which lead out through the membrane of the cell nucleus.

The problem is that the cell’s protein factories are located outside of the cell nucleus. So somehow, the blueprints for the cell’s components must be transported out of the cell nucleus to the protein factories.

So how does the information get from the cell nucleus to the protein factory?

This finding was made by the American scientist Marshall W. Nirenberg in 1959. He recognized that single blueprints are transcribed from the long DNA strand. A copying tool travels along the appropriate section of the DNA and generates an exact copy of the gene letters’ sequence. This copy is called messenger RNA because it carries the blueprint to the cell’s protein factories, just like a little messenger.

In its structure, the messenger RNA much resembles the DNA. It, too, is made up of “gene letters” in sequence (bases). However, the RNA thread only has a single strand and is much shorter. Thus, it can easily slip out through one of those pores in the nuclear envelope and find its way to the protein-building machinery.