What is genetic mutation


Changes in the genetic information of a cell are known as mutations. These can be triggered by environmental influences such as UV radiation or radioactive radiation (mutagens) or by chance during the replication of cell information.

  • either at the level of a gene,
  • at the level of the chromosomes or
  • at the genome level

Gene mutations

In the case of a gene mutation, the base sequence of individual genes changes through the exchange, insertion or loss of individual nucleotides. A distinction is made between a point mutation and a grid shift mutation. The following figures show the mutations and their effects.


Point mutations

Mute mutation
A base pair is exchanged, but the redundancy of the genetic code means that the amino acid remains the same.

Missense mutation
A base pair is exchanged and the triplet codes for a different amino acid; the spatial structure of the resulting protein can then change.

Nonsense mutation
A base pair is exchanged and the triplet now codes for a stop codon; Translation of the protein is then interrupted, the protein remains incomplete and is mostly inoperable.


Frame shift mutation

A pair of nucleotides is exchanged so that the reading frame shifts and not only one amino acid but also all of the following amino acids change.

One or more nucleotide pairs are deleted from the sequence.

One or more nucleotide pairs are inserted into the sequence (this creates a stop codon, but a triplet can also be created that codes for a different amino acid).

Chromosome mutations

A chromosome mutation changes the structure of individual chromosomes. These changes can be seen after staining the chromosomes
even see it under the microscope.

Different types of mutation:

  • Deletion: A chromosome segment is completely lost. The deleted section can then be lost or incorporated into another chromosome.
  • Duplication: A section of chromosomes is doubled. Since no genes are lost as a result, such mutations can remain relatively inconspicuous
  • Inversion: A section of chromosomes is turned over. Here, too, no genes are lost, but changing their order can have serious consequences.
  • Reciprocal translocation: Different chromosome segments are exchanged between two non-homologous chromosomes.
  • Fusion: Two chromosomes fuse together.
  • Fission: A chromosome falls apart.


Genome mutations

A genome mutation changes the number of chromosomes in a chromosome set. In humans, these mutations often mean that the developing embryo is not viable, which is why there are few diseases that are based on a genome mutation. This form of mutation is more common in plants, especially useful plants. Often they are even created consciously so that the plants are particularly resistant to diseases, parasites or environmental influences. We differentiate between

Different types of mutation:

  • polyploidy, in which the entire set of chromosomes is multiplied and
  • aneuploidy, in which only individual chromosomes are duplicated or omitted.


  • Autopolyploidy: duplication of the set of chromosomes within a species.
  • Allopolyploidy: duplication of the set of chromosomes through hybridization, i.e. when the germ cells of different species fuse with one another.


  • Monosomy: A homologous chromosome of a chromosome pair is missing (e.g. Turner syndrome: there are not two sex chromosomes, only one X).
  • Trisomy: A chromosome is not present twice (as is normal), but threefold (e.g. Down syndrome: trisomy 21, chromosome 21 is present three times).