Radioactivity, nuclear waste, chemicals, harmful environmental influences - these and other terms accompany us through all media. Increased mutation rates (mutation probability) are mentioned in this context. But what exactly is a mutation, what mutations are there, and are mutations always negative? We want to give you a brief insight into the world of genes and chromosomes.
A mutation (lat .: mutare = change) means a change of the genetic material, the genotype. It may be a qualitative or quantitative change in the structure, but also the effect of genetic factors. However, mutation is not the same as mutation. The following distinctions are made.
Somatic mutation: These are changes in all the body cells that have nothing to do with reproduction. These changes can be reflected in the growth and function of the cells. This, for example, causes cancer, and one also uses this mutation form to explain the aging process. This modification of the genetic material is "transmitted" to subsequent cells in one's own body, but can not be inherited to offspring.
Generative mutation or germline mutation: Mutations that occur in the germ cells, ie in oocytes or in the cells that produce sperm, can be transmitted to offspring.
There are three types of mutations:
- Gene Mutation or Point Mutation: A single small piece of information (gene) on a chromosome is altered. This is the result of spontaneous or environmental changes (exchange, elimination or insertion) of the base sequence of the DNA (DNA = deoxyribonucleic acid, storage form of the genetic material). There are body mechanisms to repair the DNA, but it can also cause malfunction.
- Genome mutation: change in the number of chromosome sets or chromosomes (carriers of genetic information). For example, the 3-fold instead of 2-fold presence of chromosome 21 (trisomy 21) leads to Down syndrome in humans. Genome mutations play a major role in plant breeding. Yields can be increased by multiplying the sets of chromosomes.
- Chromosome mutation: change in the shape and structure of chromosomes. These are triggered, for example, by chemical substances or ionizing radiation.
Mutations and selections as the cornerstones of evolution - Darwin's theory
"The Origin of Species by Means of Natural Selection" (short: The Origin of Species) was the book that Charles Robert Darwin published in 1859. It included the results of his studies, which he describes as follows: "Natural breeding selection is the deciding factor in the evolution of the species, and as the number of offspring is greater than that required for species maintenance, there is competition that only the adjusted will override ".
Speech ability by mutation?
Researchers recently reported on a gene (FOXP2) in the British journal Nature that may have enabled humans to communicate through language mutation (Nature 418: 869-872).
Mutations can therefore be beneficial as well as detrimental to reproduction. Only when a mutation leads to a change in the phenotype (characteristic image, appearance) does it become significant for the selection.