It appears ‘junk DNA’ isn’t so useless after all as Grace Yu delves into the latest discovery in genetics
DNA is that complex code of As, Ts, Gs and Cs that is at the core of every cell in the human body. It is a code to make the proteins, the cells, and the structures that we call our body.
In the 1970s, a scientist coined the term ‘junk DNA’ for the large portions of the DNA for which no functions were known about. This would apply to 20% of the human DNA sequence that does no coding for proteins, also known as noncoding DNA. These sequences were once considered completely useless junk, parts left in our genome that were once functionally useful in our ancestors, but have since become redundant.
It’s becoming increasingly clear, however, that what we thought was junk before is most definitely not. Over the past few decades, scientists have found valuable sequences in this junk DNA that do much more than simply sit around, coasting off the work done by coding DNA.
One of the most prominent examples of apparently useless, but life-saving junk DNA is the telomere. Telomeres are repeating sequences at the end of a string of DNA that protect our DNA from getting damaged when it is replicated in our cells. Replication often results in the ends of DNA getting chopped off and so telomeres ensure no vital, coding DNA is lost in the process.
Most recently, a research team under Dr Visel in Berkeley, California has discovered junk DNA that codes for some aspects of facial structure. This is not to say that these sequences of DNA code for how our face looks, but rather, these sequences are vital in activating those genes that do.
They may seem useless to the untrained eye, but for those looking for value among invaluable things, it is an important piece to the puzzle. These supposed junk sequences reside a long way up the chain from the sequences that actually code for our faces, but they spread their love from afar, helping to kick start the process of face making. Let’s face it; if these guys weren’t doing their job, you could bring literal meaning to the term ‘butt ugly’.
It is now well-known that certain sequences of DNA have effects on genes that code for the necessary building blocks of our bodies. It’s been said that these sequences may account for up to 98% of what is considered junk DNA. However, this is not a matter of lock and key, far from it. These sequences of DNA do not act alone to activate a gene; they work in small groups that are usually located close together in the sequence of DNA.
In many cases, it is unknown which sets of these sequences act with others to activate particular genes. It’s like picking a lock on a door, it’s not easy, and it’s not simply done with one try.
Scientists can, and have, spent years and years trying to find out what combinations of these junk DNA sequences work together to activate one single segment of DNA. Though this may seem like a ludicrous amount of effort to go through for such a small reward, the information we yield from such studies is vital to understand the way our bodies work.
Dr Visels’ team at Berkeley has identified more than 4,300 of these segments of junk DNA. Some of these segments have muted, barely useful effects, while others work together with other segments to turn on a specific coding sequence of DNA resulting in gene expression and a measurable effect.
The segments of DNA Dr Visels’ team in particular have identified, affect the shape of various parts of the face. They sculpt the finer features of the face: length, width, depth and structure; much like an artist’s hands.
Before we get too excited at the prospect of being able to genetically alter our faces, the research thus far has been focused mainly in mice. It is hoped this research can be translated to humans however, as we share a large portion of our DNA with the furry little pests and, as we are both mammals, we have very similar developmental processes.
Imagine that. A few genes clipped or added here and there and you could be a man-sized rat. Ain’t that the dream? The team is now working to identify similar DNA sequences present in the human genome, to see if their studies in mice could be applicable to humans after all.
We have come a long way in recent years, and most of this progress is due to our rampant curiosity. If scientists had simply stopped investigating junk DNA once one of them decided the stuff was useless, we would be no closer to understanding fully how genes work, and would probably be sitting scratching our heads in confusion at the whole thing.
This proves that everything in science is worth investigating further. Junk DNA holds the key to so many advances in genetic research that will be unveiled in years to come. Who knows, those spare As, Ts, Gs and Cs may even unlock the secret to belly button lint. A long shot, but anything appears to be possible.
Additional reporting by Michael O’ Sullivan