We call mutations, in biology, some changes that happen in the sequence of the nucleotides of the genetic material of a given organism. These can happen due to errors in copying the genetic material during cell division, for example, caused by exposure to ultraviolet or ionizing radiation, chemical mutagens or even viruses.
Hypermutation also occurs, which are processes in which cells end up deliberately causing mutations. When we are talking about mutations that happen in multicellular beings, we can divide them between germline mutation and somatic mutations. In the first case, the mutations are passed on to the offspring, and in the second case this does not happen.
This, however, is not fully applicable to plants efficiently, as some of them can transmit somatic mutations asexual or sexually.
When there is a mutation that was not inherited from the parents, we call it a mutation again. Its sources, however, are not related to the effects, however much the effects are related to the cells affected by this mutation.
But what are the consequences of these mutations? They end up generating, in the long run, variations in the population’s set of genes. There are unfavorable mutations, which are also known as harmful, and can end up being reduced in the population through natural selection. Favorable mutations, also known as beneficial or advantageous, can bring adaptive evolutionary changes, resulting in the evolution of the species.
Butterflies may, for example, produce offspring with new mutations, but most of them will have no effect. However, it may be that one of them changes the color of the descendants of that particular individual, creating difficulties or facilities for them to be seen by predators. When the changes that take place are advantageous, the butterfly survives and starts to produce its own offspring with the changes, constituting, over time, a new population.
Although there are favorable mutations and unfavorable mutations, there are also neutral ones. These are the ones that do not have effects that are capable of influencing the fitness of individuals. This can end up accumulating over time, however, thanks to genetic drift.
Some scientists believe that most mutations belong to this group, whose theory was developed in the book The Neutral Theory of Molecular Evolution by Motoo Kimura. In addition to this belief, most changes are corrected through DNA repair mechanisms before they actually become mutations.