Mutations are called spontaneous changes in the DNA structure of living organisms, leading to the appearance of all kinds of deviations in growth and development. So, we will consider what a mutation is, the reasons for its occurrence and the classifications that exist in science. It is also worth paying attention to the effect of changes in the genotype on nature.
What is a mutation?
Scientists say that mutations have always existed and are present in the organisms of absolutely all living creatures on the planet, moreover, they can be observed up to several hundred in one organism. Their manifestation and degree of severity depend on what reasons they were provoked and which genetic chain was affected.
Causes of mutations
The causes of mutations can be very diverse, and they can arise not only naturally, but also artificially, in laboratory conditions. Genetic scientists identify the following factors for the occurrence of changes:
1) radiation (ionizing and x-ray) - with the passage of radioactive rays through the body, the charges of the electrons of atoms change, which leads to disruption of the normal functioning of chemical-biological and physico-chemical processes;
2) an increase in body temperature can also lead to the appearance of changes due to exceeding the body's endurance threshold;
3) delays, and sometimes excessively rapid growth, are possible when dividing DNA cells;
4) “breakdown” of DNA cells, after which even in the case of restoration it is impossible to return the atom to its original state, which leads to inevitable changes.
Mutation Classification
Over 30 changes in the genotypes and gene pools of living organisms caused by mutations are read in the world, and they are not always expressed in external or internal deformities, many of them are completely harmless and do not cause discomfort. To find the answer to the question: "What is a mutation?" - You can also refer to the classification of mutogens, which are grouped depending on the causes that cause them.
1. According to the typology of the changed cells, somatic and generative mutations are distinguished. The first is observed in mammalian cells of living organisms, transmitted only by inheritance. As a rule, it is formed even during the development of the embryo in the womb (for example, different eye color , etc.). The second is more often manifested in plants and invertebrates, caused by adverse external environmental factors (growth of mushrooms on a tree, etc.).
2. At the location of the mutated cells, nuclear mutations are distinguished that directly affect the DNA (cannot be treated), and cytoplasmic - they relate to changes in all cells and fluids that interact with the nucleus (treatable or eliminated, these mutations are also called atavisms).
3. Depending on the reasons that provoked the appearance of changes, there are natural (explicit) mutations that occur suddenly and without cause, and artificial (induced) mutations - these are malfunctions in the normal functioning of chemical and physical processes.
4. Depending on the severity of the mutation is divided into:
1) genomic - changes in the number of sets of chromosomes (Down's disease) ;
2) gene mutations - changes in the sequence of nucleotide construction during the formation of new DNA chains (phenylketonuria).
The value of mutations
In most cases, they harm the entire body, as they interfere with its normal growth and development, and sometimes lead to death. Useful mutations never occur, even if they endow with superpowers. They become a prerequisite for the active action of natural selection and affect the selection of living organisms, leading to the emergence of new species or degeneration. Thus, answering the question: “What is a mutation?” - It is worth noting that these are the smallest changes in the structure of DNA that violate the development and vital activity of the whole organism.