Deoxyribonucleic Acid (DNA) not only has the blueprint for protein synthesis, but also has instructions for gene control, a new study has found.

The study, conducted by Dr. John Stamatoyannopoulos from University of Washington and colleagues shows that the DNA has a second code.

"For over 40 years we have assumed that DNA changes affecting the genetic code solely impact how proteins are made," said Stamatoyannopoulos. "Now we know that this basic assumption about reading the human genome missed half of the picture. These new findings highlight that DNA is an incredibly powerful information storage device, which nature has fully exploited in unexpected ways."

The genetic code is similar for all organisms and is stored in one of the two DNA strands as non-overlapping, linear sequence of nitrogenous bases Adenine (A), Guanine (G), Cytosine (C) and Thymine (T). These four letters are the 'alphabet' of the genetic code and are used to write code words.

The code consists of three-letter words (also called triplets or codons). There are a total of 64 codons.

Now, researchers have found that the codons, which they refer to as duons, can be used for gene control. The team says that about 15 percent of codons could act as duons and that these bilingual genetic codes have shaped protein evolution.

The latest discovery shows that there may be different facets to the genetic code. Previously, it was believed that the DNA carries instructions to make proteins, but the UW study reveals that it might even have codes to stabilize the protein. The study also explains why certain codons are preferred over other, similar codons during protein synthesis.

The research may change how scientists look for clues about a genetic disease.

 "The fact that the genetic code can simultaneously write two kinds of information means that many DNA changes that appear to alter protein sequences may actually cause disease by disrupting gene control programs or even both mechanisms simultaneously," said Stamatoyannopoulos.

The study is published in the journal Science.

You can also read an article on the current study by Robert J. Weatheritt and M. Madan Babu from MRC Laboratory of Molecular Biology, Francis Crick Avenue, Cambridge.