Mistakes by Design
Sometimes there is a purpose in apparent mistakes. Some modern art looks accidental. An earthquake scene might be part of a drill. Here are some cases in living cells of "accidents on purpose."
1. Researchers at Ohio State say that a "mistake" in a single-cell organism is actually a "rewrite essential for life." The apparent mistake involves translation of a gene in a pathogenic microbe. The RNA copy of the gene is edited by the organism before splicing occurs -- called noncanonical splicing. Without the edit, the splicing required for functionality does not occur, and the organism dies.
The editing described here is a swap of three nucleotides for three others that, according to the rules of biology, do not belong where they end up. This is why it looks like a mistake. (Emphasis added.)
This particular edit, involving a "swap of three nucleotides for three others that are completely out of place," has not been observed before. What looked like a mistake is essential for survival of the organism.
2. As ENV readers well know by now, "junk DNA" is itself a junked concept. Geneticists have found many different functions in non-coding DNA that previously looked like mistakes -- leftover evolutionary junk with no purpose. Another example came to light in this from the Wellcome Trust Sanger Institute. Researchers looked for non-coding regions that appear to be under purifying selection, indicating they are important to the organism. They may not understand the function, but can tell by watching what happens when mutations occur:
The team found that some non-coding DNA regions showed almost the same low levels of variation as protein-coding genes, and called these 'ultrasensitive' regions.
Within the ultrasensitive regions, they looked at specific single DNA letters that, when altered, caused the greatest disturbance to the genetic region. If this non-coding, ultrasensitive region is central to a network of many related genes, variation can cause a greater knock-on effect, resulting in disease.
3. Most of us view traffic jams as necessary evils, if not mistakes. Cells have traffic jams, too, when cargo-carrying machines become crowded on their miniature intracellular highways. The dynein or kinesin motor cars come to a grinding halt. There may be more of a method in that madness, though, than on our freeways. In Current Biology, "Intracellular Transport: The Causes for Pauses," Kathlyn M. Trybuss explains newly understood reasons for the pauses. To summarize, she writes:
Intracellular transport of motor-driven cargo faces the navigational challenges of a dense, intersecting cytoskeleton and obstacles including organelles. A new study investigates why directed early endosome trafficking is so frequently interrupted, and how pauses play a role in cargo sorting.
She describes how the little motorcars can run continuously in vitro. It didn't make sense that they would pause so often inside the cell, so some researchers set up obstacle courses in their test-tube setups to find out why. They wanted to see if the pauses have a biological role. It appears they do.
Several possibilities emerged from the study. The cargo trucks appear to be involved in creating tension to structure the endoplasmic reticulum, a site where finishing touches are put on proteins. It also appears that multiple motors perform cargo splitting or fusion as they engage in miniature tug-of-wars with motors on different microtubules. "Tension generated by this mechanism may also be biologically relevant for endosomal fission and cargo sorting for either recycling or degradation," Trybuss explains.
In short, what looks like inefficiency or mistakes, turns out to have a purpose. Trybuss ends:
The idea that these interruptions in transport play a biological role in facilitating early endosome fusion and fission, as well as maintenance of ER structure, is novel. Mother Nature yet again shows us her artistry, making meaningful use of the pauses between the directed organelle runs.
Here we have three examples of apparent mistakes that turned out to have beneficial functions. We see this kind of phenomenon in human design. As noted above, a disaster scene might be purposely staged to let emergency crews practice. Art that looks chaotic may convey a philosophical message from its creator. Construction zones with cones and flashing lights may be interruptions to improve construction.
This suggests that biology would be well served by assuming design until the case is proven to be otherwise. More often than not, it's been a safe bet to begin with the assumption: "If it works, it's not happening by accident."
Photo credit: David Coppedge.