## What can a mutation really do?

When talking about genetics, one of the tropes most frequently used in science fiction is mutation. Mutations cause a change in the properties of various creatures (often they are people, but it is not a rule), which subsequently play important roles in stories. If we were to ask ourselves the question: "What superpowers can a genetic mutation really bring to a person?", the answers would be much simpler than those usually presented on the silver screen. It is obvious that since the final product of the expression of each gene is a functional RNA or a protein, mutations primarily affect the properties of these molecules. It follows that the mutation can never cause "laser sight" or "magnetic skin". However, mutations can really bring new, previously unseen abilities to people – for example, lactose intolerance is a completely standard feature of adult people, since milk is primarily the food of mammalian newborns. In the past, however, a mutation appeared in the human population, thanks to which the human body produces the enzyme lactase (it enables the digestion of milk sugar) even in adulthood, and thus we can consume milk throughout our entire lives. As this mutation spread through the human population, milk can now be consumed by many adults, although few would call this ability a "superpower" (for more information on lactase and other examples of mutations that contribute to ongoing human evolution, see chapter 14 – the principle of evolution).

A similar phenomenon can also be observed in the human body's ability to tolerate higher amounts of alcohol in drinks. In Asian populations we can very often come across a variant gene encoding the alcohol dehydrogenase enzyme, which allows the decomposition of ethanol into toxic acetaldehyde several times faster than the wild type allele. Thanks to this enzyme variant, it seems that Asian people get drunk much more easily. Conversely, mutations that slow down the production of acetaldehyde make it easier for people to tolerate higher amounts of alcohol. In a similar way, mutations in some genes allow the inhabitants of the Himalayan regions to survive at extremely high altitudes, even though there is significantly less oxygen in the air in those places. On the other hand, just as a mutation (or a combination of several mutations) can help our body to adapt to a particular type of environment, it can also cause certain RNAs or proteins inside the body to not function correctly. As a result of these mutations, many types of metabolic diseases (e.g., phenylketonuria), and food intolerances, but also other serious genetically determined diseases occur. Mutations can indeed bring new abilities to a person, but rather than the ability to bend steel beams with one's hands, we should imagine the ability to metabolize milk or alcohol without difficulty.