04 Classification of genetic mutations
A mutation is a sudden change in the nature of the factors that determine particular characteristics, which may result in a change in the characteristics of the organism.
By inheritance
- True mutation: is inherited through successive generations.
- False mutation: disappears with the death of the individual and is not passed to offspring.
By importance
- Desirable mutations — rare: e.g. the Ancon breed of sheep with short curved legs that cannot climb fences, doubled crops of wheat and fruit, and increased penicillin yield.
- Undesirable mutations — common: cause congenital deformities, sterility, hereditary diseases and reduced yield.
By location
- Gametic mutation: occurs in the reproductive cells and gametes, so it appears in the children and the coming generations.
- Somatic mutation: occurs in a body cell and appears as a branch with new characteristics in a plant — called a branch mutation — which is propagated vegetatively.
By type
- Gene (point) mutation: a change in the chemical structure of a gene by rearranging or substituting a nitrogenous base, which changes an amino-acid codon so that a different protein is produced and a new character appears.
- Chromosomal mutation — numerical: gain or loss of a chromosome, or polyploidy (3n, 4n). Structural: gain or loss of a chromosome segment, or a segment breaking, rotating 180° and rejoining inverted, or exchange of parts between two non-homologous chromosomes.