Mutational variability
Mutations are abrupt and persistent changes in traits that are inherited.
All mutations have the following properties:
- come on suddenly;
- arise in individual individuals;
- can be recessive or dominant;
- the same mutation can be repeated.
Each mutation is caused by the action of environmental factors, which in most cases cannot be accurately determined.
Example:
albinos sometimes appear in populations of many animal species.
Allocate gene mutations (caused by a change in a gene, i.e., a violation of the sequence of nucleotides in DNA), chromosomal (associated with a change in the structure of chromosomes) or genomic (caused by a change in the number of chromosomes in a karyotype).
Mutational variability creates new genes or changes existing ones, thereby enriching the gene pool of the population.
Mutation of each individual gene rarely occurs in nature. But the number of genes in the genotype is large (in higher forms, for example, there are tens of thousands of them). There are many individuals in the population, and it has existed for a long time. As a result, it turns out that each population is saturated with mutations. Scientists estimate that in some species, 10 to 25% of gametes carry mutations.
Mutational variability plays an important role in the evolutionary process. By themselves, mutations do not lead to the development of a population or a species, but they serve as a source, material for their evolution.
Dominant mutations are immediately subject to selection. Recessive mutations do not immediately manifest phenotypically. Gradually accumulating in the population, they appear in a homozygous state and also find themselves under selection pressure. If a mutation increases the organism’s adaptation to the environment, it is preserved, and if it decreases, it is removed.
Mutational variability is widely used in breeding. Under experimental conditions, mutagenic factors are used to obtain mutations – radiation exposure, chemicals, etc. Thus, the entire variety of varieties of ornamental plants is created on the basis of spontaneous or induced mutations.
Example:
a huge number of tulip varieties with different flower colors have been created.
