Text 9. The Gene Code

Prokaryotes and eukaryotes share the same 'language of life'. Comparisons of DNA sequences with the corresponding protein sequences reveal that (with a few exceptions) an identical genetic code is used in both prokaryotes and eukaryotes. This means that bacteria can be genetically engineered to make human proteins. The universal nature of the code suggests that all living things are descended from a single pool of primitive cells which first evolved this code.

One of the most remarkable facts of life is that each cell in an organism contains all the information required to determine all the characteristics of that whole organism. This information is stored in DNA, and is known as the genetic code. Deciphering that code has been one of the major scientific breakthroughs of the twentieth century. It has given us anunderstanding of how genes function, and it has opened the way for most of the recent developments in genetic engineering and biotechnology.

Transcribing the genetic code from DNA to mRNA

The genetic code is held in the order of bases along the DNA molecule. Sections of DNA called cistrons (commonly referred to as genes) contain the information needed to make a particular polypeptide. However, DNA does not carry out polypeptide synthesis directly. When the DNA in а cistron is activated, the information is transferred to a molecule of ribonucleic acid (RNA) called messenger RNA (mRNA), which acts as a template for the synthesis of the polypeptide.