Cienciaes.com: Science "makes a mistake"

2021-02-04 13:12:43

We rarely ask ourselves why we have two arms, instead of three or four, and why five fingers, instead of just one. These questions have been on the minds of biologists and molecular geneticists for years now. For example, an old article published in the humorous scientific magazine The Journal of Irreproducible Results mentioned the advances in molecular genetics that awaited us in the future. Among them, the author speculated with the creation of improved species, such as chickens that had six or eight thighs, which would avoid family fights at dinner time, since, as is well known, we all prefer to eat one, or better two, thighs if we get the chance.

Reality is responsible, as so often, to overcome fiction. Some time ago, anatomical malformations were discovered in the United States in certain wild frogs that had an increased number of hind limbs. The animals showed three or four legs, or parts of them. The worst thing was that these deformities did not seem to be the result of an experiment to make leg soup cheaper, but rather everything pointed to some effect of environmental contamination on the morphological (shape) development of these animals. The finding, of course, caused some concern, since these malformations in amphibians could portend malformations in animals that may be dearer to us: our own children.

But what determines the shape of our bodies? Why do we have two legs and not three? To understand this, we must keep in mind that our bodies are like a giant children’s construction set, made up of billions of different pieces: our cells.

We know that cells have their own design instructions, contained in the ADN of its genes and we also know that the instructions that each cell reads tell it to communicate with its neighbors and send them in turn behavioral instructions. Cells communicate molecularly with each other, they organize themselves, and each one literally decides which is going to be bigger, whether it is a brain cell or a skin cell, for example, and this without conflicting with its companions. Each cell assumes a role, as if it were actors in a play, actors who agreed to represent the play (the body of an animal) following a script that each one had written inside.

In a study, Dr. Lewis and colleagues at the University of Wisconsin in the US discovered the operation of two genes that control the number of legs in the red flour beetle. By modifying those genes, they have been able to, in effect, increase the number of legs on that animal.

Although the genetic identity between insects and higher animals, among which I dare to include the human being, is greater than we would like, there is still a long way to go to discover which genes are responsible for controlling the number of thighs of a chicken. However, I have no doubt that, since it is a question of legs, everything will work out and science will also discover that secret. Advances in obtaining sequences of the entire genomes of various animals and comparing them with each other will allow us, for example, to find out why a cat and a tiger are so similar in their morphology and so different in size, as well as other secrets. of animal morphology. However, given the implications that these works may have for the future of humanity, I believe that we will have to proceed with caution, we are not going to screw up, or, in this case, the legs.

Very good. So far, the situation of science in the year 2000 with respect to the genes that are responsible for generating the correct form of animal organisms of the different species has been briefly reflected. Much progress has been made since then. To begin with, the reason for the increase in the number of legs in the amphibians that I mentioned before was found, I think in 2002. It is a combination of factors that involved environmental contamination, but also the effects of a parasite of these animals on their metamorphosis from tadpoles to adult animals.

We still certainly don’t know everything about the development of animal form, or else we would possibly be able to engineer new animals, which have never existed in nature, or resurrect extinct animals based on their morphology. Understanding the generation of size and shape of animals would give us that power. We don’t have it yet. New artificial intelligence technologies, applied to the comparative analysis of the genomes of hundreds of species, will probably make it possible to extract the relevant information that explains, as I suggested before, why a cat and a tiger are so similar in their body proportions, but so similar. different in size. Of course we will not only obtain information about this, but about many other things that species share or that make them different. It is possible that this information will allow us to draw up a much more detailed tree of life and will allow us to reconstitute much better what has happened so that, from the first bacterium that emerged on our planet, we have reached the highest levels of epidemiological misery, as such. Maybe I would say Groucho Marx today, if this genius of humor were still among us.

Jorge Laborda.

Works by Jorge Laborda.

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