"Junk"DNA as a genetic decoy

It is well known [1, 2, 3] that in most species a large proportion of the genome does not appear to code genes or proteins, or even regulate coding DNA. This leads to the descriptive expression " junk DNA ". Naturally, it is possible that the hidden information in this DNA has simply escaped us so far; however that such sequences have high redundancy (they may, for example, be long repetitions of the same base) gives weight to their characterization as junk. This raises the question: if junk DNA is indeed useless, what might be its evolutionary advantage? An obvious answer is that there is no evolutionary advantage to junk DNA; however its presence doesn't cause any harm either. In particular the extra metabolic activity it implies may be negligible, because the percentage of metabolic activity associated with DNA replication is very small. Since only features harmful to survival or reproduction are selected out, a neutral accessory such as junk DNA could still survive. This is certainly a factor [4], and in some insects it has been shown that the genome size is related to the ability to eliminate DNA. However, for it to be the complete answer to this question one would need to prove that eliminating junk DNA by chance (i.e. by random mutation) carries a suitably low probability in all species. Also it is not always true that the energy cost associated with DNA replication is negligible [5]. A much more interesting possibility is that junk DNA may be a positive evolutionary feature, even though it serves no useful direct purpose. In this short note we suggest that its role is to protect the gene. Most significantly its presence may baffle the actions of mutation agents, such as retro-viruses. In the presence of large amounts of junk, a random genetic agent hits junk most of the time; the meaningful pieces of the genome meanwhile " hide " in the foliage. The higher the percentage of junk the higher the protection it affords to directly useful DNA. The validity of this argument is far from general. It must certainly be part of the story regarding retroviral insertions, which can indeed be found within junk DNA (along with the low-information sequences mentioned above). According to our hypothesis such insertions are missed hits. However the argument is not so clearcut (and in some cases has to break down) with regards …