useful economic features. The harmful consequences of mutagenic factors
are object of study by Ecological genetics.
Classification of the Mutations
It should be definitely said that up to now there is no comprehensive,
uniform and generally accepted classification. Those existed in the
literature can be reduced to three main groups: a) according to the way of
their arising; b) according to genotype; c) according to phenotype.
Classification according to the way of their arising. Depending on
that they are natural (spontaneous) and artificial (induced). Natural or
spontaneous mutations arise without human participation, under the influence
of different natural factors — earth and cosmic radiation, chemical
substances and other components of surroundings, changes of genetic
material, as well as some metabolites in the cells obtained as a result of
biochemical reactions. Artificial mutations arise through purposeful influences
by man using different physical, chemical and biological factors. That is why
they are called induced. On principle, there is no difference between
spontaneous and induced mutations, since their genotype and phenotype
appearance is similar. They differ only in mutation frequency, which in
spontaneous mutations is lower compared to that in the induced ones.
Classification according to genotype. It includes the changes in the
structure of genes and chromosomes, as well as in the genome, that lead
to changes in features and characteristics of the cells and organisms.
According to this classification mutations are divided into gene,
chromosome and genome (Table 8).
