Mutation

Selection Factors

A mutation (Latin mutare = change) means the change of the genome.

First of all, three different types of mutations have to be distinguished.

 Gene mutation: alteration of a single gene

 Chromosome mutation: alteration of chromosome structure

 Genommutation: change in the number of chromosomes

Mutations have two characteristics. They occur randomly and undirectedly. This means that their appearance has no direct purpose.

In addition, mutations occur spontaneously in time. However, the probability of mutation can be significantly increased by so-called mutagens. These include chemical substances, radioactivity, UV radiation and X-rays.

Mutation as an evolutionary factor

Mutation is one of the most important evolutionary factors, as it allows new alleles to enter the gene pool of the population. A mutation may be beneficial, disadvantageous or insignificant for an individual.

If a mutation is beneficial to an individual (e.g., improved water absorption of a cactus in the Sahara or human lactose tolerance), it has an advantage over the other individuals who do not possess this mutation. As a rule, this mutation will then spread within the population because increased fitness will result in the individual's genes being brought more frequently into the next generation. In this way, mutations spread in the population.

However, if a mutation is a disadvantage, it can, in the worst case, mean death, such as when vital metabolic processes are affected. Mutations that have neither positive nor negative consequences are also called silent mutations. Because a mutation can also happen in places in the DNA that contain no important information or the mutation does not change the sequence of amino acids in the genetic code, because many amino acids allow different coding (see code on the right)

This should be distinguished from the neutral mutations. There may indeed be a phenotypic expression, but this is not important for the selection. Blue eyes in humans are an example of this. This mutation has surfaced about 10,000 years ago.

Further examples of mutations in evolution

 Lactose tolerance in humans

The ability to break down milk sugar (lactose) with the help of the enzyme lactase is based on a mutation. Normally enough lactase is produced by the body only in infancy in order to digest the breast milk. Scientific research suggests that this mutation occurred between the time of Stone Age and the beginning of livestock breeding and offered a considerable selection advantage, since it was suddenly possible to ingest and utilize animal milk.

 Industrial melanism

The birch tree is in its original form a white butterfly whose habitat u.a. Birch trunks includes. He is virtually invisible on these and so optimally protected against predators. When industrial time was in full swing in the 19th century, the black soot colored the white birch trees. The birch tree was no longer protected and was recognized and eaten by its predators. Thanks to a mutation, however, black birch trees appeared, which were perfectly adapted to the now black birches and thus ensured the survival of the species.

 Red-green color blindness

In the case of red-green eyesight, sufferers have the problem of distinguishing the colors red and green. The reason for this is the change in the amino acid sequence, which is responsible for seeing colors. The important protein opsin is not properly formed and there is an altered perception of the colors red and green.

Summary

A mutation changes the genetic material

Mutations occur randomly and undirectedly

Mutagens can significantly increase the likelihood of a mutation

Mutation provides biodiversity and more variability, making it one of the key evolutionary factors