DNA CODE…EXTRA DNA…DNA JUNK
Much of the remarkable progress in biological sciences during the past five
decades following the unravelling of DNA code structure has been based on the so called
“central dogma of molecular biology” which provides a formal basis to
understand the flow of information from genes to phenotype. A strong faith
in the “central dogma” has resulted in a common belief that any sequence
of DNA code or a gene is of relevance only if it has a protein-coding function and
consequently, a significant proportion of molecular biological studies during
the past few decades have been propelled by the concept that the non-coding extra
DNA is “DNA junk” or “selfish” or “parasitic”.
On the other hand, sequencing of genomes of large number of species, ranging from bacteria to human, has clearly re-established the earlier inference of classical geneticists and cytologists that much of the DNA code in genomes of higher organisms does not carrytypical “genes” or protein-coding genetic information. As the biological complexityhas increased with evolution, the proportion of DNA code in the genomethat does not code for protein (extra DNA) has also increased. Thus while non-coding, or extra DNA “junk” is almost non-existent in bacteria, it can make up as much as 90% or more ofthe genome in higher organisms like mammals.Is the non-coding extra DNA “junk” in our genomes really “DNA junk”, whose accumulationto such high proportions reflects some kind of “failure” of natural selection, or is it a necessity for the biological complexity? It is now clear that the genetic differences between any two related species are mostly due to changes in the “non-coding” extra DNA junk rather than in the protein-coding genes. Thus while human genome has 25 fold more DNA code compared to the fruit fly, the protein coding genes appear to be only 2.5-fold greater. The evolutionary increase in biological complexity is thus not due to a greater variety of proteins butdue to more complex regulatory circuits that allow a greater variety of combinationsof similar numbers of proteins so that more complex structures and organizations can come into being. Thus it is obvious that extra DNA is not DNA junk, and may in fact be the key to our transformation as it carries much higher levels of frequency transmission/receiving capacity. Activating DNA “Junk” may be the most important access to enlightenment we possess.