Do you know the cool guy, the one that takes all of the attention and everybody likes?
Well, that’s the exome in DNA.
However another character hides behind the curtain, which was – back in the days of its discovery (in the 60s) – snubbed as “junk DNA”. Why? Because its regions don’t code for proteins, which was the only and ultimate function expected for DNA – at least at that time. However this “junk” is quite hard to ignore: it represents a huge part of the whole human DNA (98% !). How come that such huge amount of useless material inside each cell of the body has passed through evolution? So, let’s face it: possibly we have underestimated the role of “junk DNA”. A closer look at the features of non coding regions reveals a bit more about its role.
The role of non coding regions emerges loudly when comparing the genomes of different species (a practice known as comparative genomics). It is clear that simpler unicellular organism like bacterias (prokaryotes) have a fairly smaller portion of non coding DNA. Among eukaryotes (a bit more complex organisms with their DNA inside a nucleus), the genome size and the related portion of non coding regions follows the complexity of the organism too, but it hides many surprising exceptions. For as unfair as it sounds, seemingly simpler organisms as the salamander and the lilies have ten times more the amount of our DNA. Pretty lame, right? At least we can cheer up that, thanks to the non coding regions too, we improve our skills compared to a unicellular organism such as the bacteria.
Non coding regions then seem to help to communicate the complex message stored in the DNA. To understand better their role, we can see DNA as a language with its own grammar and specific elements.
The simplest ones are those that convey concepts i.e. nouns and verbs, which in the case of DNA are the exons and genes, which store the information for proteins. In both cases, they represent the core of the message – without them, there is nothing to communicate.
However, a message build merely with these blocks is extremely simple – like a telegram:
If we want to convey more complex thought, we need other elements that organize the message and enhance its communication capabilities. This is the role of different non coding regions. Keeping the parallelism with the grammar of a language, we can recognise:
1) Spacing or safe separator, which in the case of DNA function as damper or shock absorber, keeping genes and other important regions at a safe distance. Mutations then have fewer chances to affect these regions or, even worse, an entire set of subsequent genes.
cell are proteins enter nucleus dna stored bind regions regulating degree production proteins
2) Adverbs and adjectives, which define several features of the main message i.e. where, when, how etc. In the case of DNA, these regions regulate the production of proteins defining in what type of cells it must happen, at what time and how much protein must be produced.
inside the cell there are proteins that enter inside the nucleus where the dna is stored here they bind non coding regions of the dna regulating the degree of production of other proteins
3) Punctuation and conjunction, which coordinate the reading defining the beginning, and the end of a sentence, its pauses and the connection between elements. In the case of DNA too, there are regions that mark the beginning and the end of a gene and its connection with the other regulatory elements.
Inside the cell, there are proteins that enter inside the nucleus, where the DNA is stored. Here they bind non-coding regions of the DNA, regulating the degree of production of other proteins.
Both coding and non coding regions are equally essential for the final message: but only the second enable to express and perform complex functions. We know quite little about non coding regions, but the more we dig into them, the more essential their role appears.