Pros and cons of genetic mutations. Useful mutations Mutations pros and cons

What is a mutation? This, contrary to misconceptions, is not always something scary or life-threatening. The term refers to a change in genetic material that occurs under the influence of external mutagens or the body’s own environment. Such changes can be useful, not affect the functions of internal systems, or, on the contrary, lead to serious pathologies.

Types of mutations

It is customary to divide mutations into genomic, chromosomal and gene mutations. Let's talk about them in more detail. Genomic mutations are changes in the structure of hereditary material that radically affect the genome. These include, first of all, an increase or decrease in the number of chromosomes. Genomic mutations are pathologies that are often found in the plant and animal world. Only three varieties have been found in humans.

Chromosomal mutations are persistent, abrupt changes. They are associated with the structure of the nucleoprotein unit. These include: deletion - loss of a section of a chromosome, translocation - movement of a group of genes from one chromosome to another, inversion - complete rotation of a small fragment. Gene mutations are the most common type of change in genetic material. It occurs much more often than chromosomal.

Beneficial and neutral mutations

Harmless mutations that occur in people include heterochromia (irises of different colors), transposition of internal organs, and abnormally high bone density. There are also useful modifications. For example, immunity to AIDS, malaria, tetrochromatic vision, hyposomnia (reduced need for sleep).

Consequences of genomic mutations

Genomic mutations are the causes of the most serious genetic pathologies. Due to changes in the number of chromosomes, the body cannot develop normally. Genomic mutations almost always lead to mental retardation. These include trisomy of chromosome 21 - the presence of three copies instead of the normal two. It is the cause of Down syndrome. Children with this disease experience learning difficulties and are delayed in mental and emotional development. The prospects for their full life depend, first of all, on the degree of mental retardation and the effectiveness of activities with the patient.

Another terrible deviation is monosomy of the X chromosome (the presence of one copy instead of two). Leads to another severe pathology - Shereshevsky-Turner syndrome. Only girls suffer from this disease. The main symptoms include short stature and sexual underdevelopment. A mild form of oligophrenia often occurs. Steroids and sex hormones are used for treatment. As you can see, genomic mutation is the cause of severe developmental pathologies.

Some chromosomal pathologies

Hereditary diseases caused by mutation of several genes at once or any violation of the chromosome structure are called chromosomal diseases. The most common of them is Angelman syndrome. This hereditary disease is caused by the absence of several genes on the 15th maternal chromosome. The disease manifests itself at an early age. The first signs are loss of appetite, absence or poverty of speech, constant unreasonable smile. Children with this pathology experience difficulties with learning and communication. The type of inheritance of the disease is still being studied.

A disease similar to Angelman syndrome is Prader-Willi syndrome. Here, too, there is a lack of genes on the 15th chromosome, but not the maternal one, but the paternal one. Main symptoms: obesity, hypersomnia, strabismus, short stature, mental retardation. This disease is difficult to diagnose without genetic testing. As with many hereditary diseases, complete therapy has not been developed.

Some gene diseases

Gene diseases include metabolic disorders caused by a monogenic mutation. These are disorders of the metabolism of carbohydrates, proteins, lipids, and the synthesis of amino acids. A disease familiar to many, phenylketonuria, is caused by a mutation in one of many genes on the 12th chromosome. As a result of the change, one of the essential amino acids, phenylalanine, is not converted into tyrosine. Patients with this genetic disease must avoid any food containing even small amounts of phenylalanine.

One of the most serious connective tissue diseases, fibrodysplasia, is also caused by a monogenic mutation on chromosome 2. In patients, muscles and ligaments become ossified over time. The course of the disease is very severe. A complete treatment has not been developed. The type of inheritance is autosomal dominant. Another dangerous disease is Wilson's disease, a rare pathology that manifests itself as a disorder of copper metabolism. The disease is caused by a gene mutation on chromosome 13. The disease is manifested by the accumulation of copper in the nervous tissue, kidneys, liver, and cornea of ​​the eyes. At the edges of the iris you can see the so-called Kayser-Fleischner rings - an important symptom in diagnosis. Usually the first sign of Wilson's syndrome is abnormal liver function, its pathological enlargement (hepatomegaly), cirrhosis.

As can be seen from these examples, gene mutation is often the cause of serious and currently incurable diseases.

Beneficial Mutations

Katerinka

Of course, there are, with the help of mutations, new strains of bacteria that are resistant (resistant) to antibiotics can arise. With the help of mutations, many varieties of plants and animal breeds have been developed (although this is only useful for humans). Mutations create a reserve of hereditary variability. When environmental conditions change, some mutations turn out to be beneficial... For example, flies on the Pacific Islands. During strong storms, most of them died - they were carried out to sea and their wings were broken, but some of the flies with short wings (mutants) survived.

Alexander Igoshin

So all evolution is based on beneficial mutations. For example, let’s take a population of some animals, suddenly for some reason they began to lack food, a mutation associated with a decrease in body size would be useful here. Or some group of animals has an enemy-predator, then a useful mutation is an increase in running speed.

Larisa Krushelnitskaya

Well, for example, humans have 5 times larger brains than chimpanzees. This is a beneficial mutation. The gene that is responsible for this mutation was discovered when comparing the genomes of humans and chimpanzees.

And in general, almost any sign that distinguishes an individual from fairly distant ancestors is the result of a mutation. Wings in birds, skeleton in fish, mammary glands in mammals, lungs in lungfish, etc.

other presentations on the topic “Pros and cons of genetic mutations”

“Types of mutations” - Useful +. Harmful -. Loss. Gene (spot). Duplication. Mutation. Aneuploidy. Modification. Mitosis, meiosis, fertilization. Mutant. Deletion. According to the location of the mutation. Combinative. Occur in germ cells. Polyploidy. Genetic material. Mutations can be both harmful and beneficial.

“Genetic diseases” - Many descendants of Queen Victoria suffered from the disease. Hereditary diseases caused by the presence of a defect in genetic material. Russia was no exception. Human genetic diseases are inherited. DNA analysis revealed traces of hemophilia. This was typical for many royal and royal families.

“Genetic connection” - How to obtain the complex substance copper (II) oxide from the simple substance copper? Grounds. The sum of all coefficients is equal. Define the concept of “Genetic connection”. H3PO4. Al2O3. It's called a genetic series. Salt. NaOH. Write down reaction equations. HCl. Metal. Classification of inorganic substances.

"Mutation" - Homologous mutations. “Once upon a time there was a tailless cat who caught a tailless mouse.” Mutations occur randomly in nature and are found in descendants. A mutation in Japanese waltzing mice causes strange spinning and deafness. Classification of mutations. Recessive mutations: nude \left\ and hairless \right\.

“Gene mutations” - Mitochondria have their own circular DNA. A mutation in an important connective tissue protein, fibrillin. Gene properties. Thus, about 1000 mutations of the cystic fibrosis gene have been identified, most of them rare. The names of gene diseases are not systematized (approach 3). Each mutation receives a 6-digit number. The most common mutation is the loss of 3 nucleotides (triplet 508).

Relevance of the topic Recently, I was watching TV and saw a program about a group of scientists - geneticists who were talking about genetic mutations. Some have argued that genetic mutations are the “plague of the 21st century.” Others saw nothing wrong with it. I decided to weigh all the pros and cons of genetic mutations.

Genomic mutations are a change in the number of chromosomes in the genome. Polyploidization The formation of organisms or cells whose genome is represented by more than two sets of chromosomes. Radioactive radiation, the action of pesticides, high or low temperature lead to disruption of the divergence of chromosomes to the poles of the cell during mitosis or meiosis. Aneuploidy (heteroploidy) A change (increase or decrease) in the number of chromosomes that is not a multiple of the haploid set. There is no divergence of the chromatids of individual chromosomes during mitosis, or of individual homologous chromosomes in meiosis.

Chromosomal mutations - changes in the structure of chromosomes Deletion Loss of a section of a chromosome. The causes of these mutations are different: disturbances that occur during meiosis, during cell division, as well as breaks in chromosomes and chromatids and their reunification in new combinations, in which the normal structure of the chromosome is not restored. Lead and mercury salts, formaldehyde, chloroform, and drugs for controlling agricultural pests can provoke these mutations. Translocation A change in the position of any part of a chromosome in the chromosome set. The basis is the mutual exchange of sections between two non-homologous chromosomes, the movement of a section within the same chromosome (intrachromosomal transposition) or to another chromosome (interchromosomal transposition). Duplication (doubling) Doubling of a chromosome fragment, when one of the sections is represented on the chromosome more than once. Inversion A 180° rotation of individual chromosome sections, as a result of which the gene sequence in the inverted section changes to the reverse. Centric fusion Fusion of non-homologous chromosomes.

Gene (point) mutations A change in the nucleotide sequence of a DNA molecule in a certain region of a chromosome. Exposure to chemical mutagens, UV rays. 2. By place of occurrence Somatic mutations Occur in somatic cells Exposure to chemical mutagens, UV rays Generative mutations Occur in the cells from which gametes develop, or in germ cells. Exposure to chemical mutagens, UV rays 3. According to adaptive value Harmful mutations Sharply reduce viability (semi-lethal). Mutations leading to death. Radioactive radiation, exposure to pesticides, drugs. Beneficial mutations Serve as material for the evolutionary process and are used by humans to breed new varieties of plants and animal breeds. They occur rarely - one in hundreds of thousands of cases.

Genetic diseases Characteristics Examples Congenital Caused by various harmful factors that affect the expectant mother during pregnancy Some congenital diseases are inherited. They rank first in mortality. Fetal alcohol syndrome is a deviation in the psychophysical development of the child, the cause is the woman's consumption of alcohol before and during pregnancy. The syndrome is a leading cause of intellectual disability. Down syndrome is a form of genomic pathology in which the karyotype is most often represented by 47 chromosomes, since the chromosomes of the 21st pair are represented by three copies. Hereditary diseases Caused by chromosomal and gene mutations. They can appear at any age, but are more common in children. Hereditary diseases are not affected by mutagenic factors. Alzheimer's disease. Symptoms: confusion, irritability and aggressiveness, mood swings, impaired ability to speak and understand what is said, and loss of long-term memory. Parkinson's disease is a chronic disease characteristic of older people. Caused by the progressive destruction and death of neurons in the substantia nigra of the midbrain and other parts of the central nervous system, it is characterized by motor disorders, autonomic, and mental disorders. midbrain neurons Acquired diseases Acquired during life. They can smoothly flow into hereditary ones. Some acquired diseases remain with the owner, while others pass quickly. Anosmia is loss of sense of smell. Partial anosmia to some substances is more common. sense of smell

Conclusion: Studies on various objects have shown that the phenomenon of mutational variability is characteristic of all organisms. Mutations affect various aspects of the structure and functions of the body. Currently, the following types of mutations are distinguished: genomic, chromosomal, gene. Genetic mutations include, first of all, diseases associated with them. All genetic diseases are divided into 3 groups: congenital, hereditary, acquired. There is some reason for the mutation, although in most cases it is impossible to determine. The number of mutations can be sharply increased by influencing the body with so-called mutagenic factors. Most mutations are harmful to the body, but there may be neutral and beneficial mutations. Scientists have found that our body independently mutates when fighting many diseases; in addition, scientists create medicines that prevent us from dying from the simplest diseases (colds, flu, etc.), and this is also a mutation.

The Planned Parenthood test examined the DNA of men and women. It involved 2,500 men (48%) and women (52%) aged 20 to 45 years. The results were disappointing: every second person has a genetic predisposition to serious diseases. Scientists believe that the presence of such mutations does not necessarily lead to disease or even be inherited. The danger increases when the parents have the same mutation. To understand this issue, Pravda.Ru turned to Marina Fridman, tocandidate of biological sciences,nauchnwowemployeeatInstitute of General Genetics RAS.

— Almost half of Russians are carriers of genetic mutations. How dangerous is this for their offspring?

- This is a very useful study; but, firstly, there is nothing new or catastrophic in its results. Each person and humanity as a whole are carriers of several lethal or particularly harmful mutations. In some cases, certain mutations are more common. For example, these could be neurological diseases that develop only in certain areas. And there are a variety of reasons for this.

— Do modern techniques allow us to correct genetic mutations?

— Genes can be corrected, but, unfortunately, this process is still fraught with a large number of errors. Therefore, as a rule, this is done in cases of risk of hereditary diseases. The problem is usually solved with IVF. Healthy eggs and sperm are selected that do not carry the corresponding mutation. Such technologies already exist.

In some cases, there may even be a situation where these mutations are not recessive. If, say, they are associated with the X chromosome, then only boys will be born sick. If you ensure fertilization with sperm with a Y chromosome, the born will be healthy. These will be girls.

— Are there methods that allow future parents to minimize the risk of genetically transmitted diseases in their children?

— Various tests already exist. For example, newborns can now be tested for phenylketonuria, an inherited disorder of amino acid metabolism caused by a deficiency of liver enzymes. It is a genetic disease, but a recessive one.

Here's a concrete example. If the purity of a particular disease is increased in a given population, then it should be tested either in the parents for carriage or for the presence of the disease in newborns. Because in some cases - such as with phenylketonuria - if measures are taken in time, it can usually be prevented.

— What diseases are most often transmitted genetically?

— Almost all severe and moderately severe diseases are determined by a large set of genetic and non-genetic factors: hypertension, a tendency to heart attacks, strokes, type 2 diabetes. In Russia, as in other countries, the practice of genetic counseling has long existed. Traditionally, people who have either already had a sick child or have a sick family member can be referred for genetic counseling.

For example, if they have already had a child with Down syndrome, then they can determine whether other children are likely to have this disease. The fact is that with most forms of this disease, the likelihood of having a sick child again is very low. Nevertheless, there are still chromosomal variants in which there is a possibility of re-birth of an affected child.

Chromosome analysis of the parents allows us to show which variant we are dealing with - the first or the second. That is, can they give birth to a second healthy child - or are they again likely to have a sick child again? Perhaps in this case it makes sense to resort to IVF and make sure that the fertilized egg turns out normal.

Interviewed by Lada KOROTUN

Most mutations are harmful or have little economic significance. Singleton pointed out that mutation breeding has produced some valuable plant lines.

He spent a lot of time and effort studying the effect of constant or prolonged gamma irradiation on mutation rates. This was done using Co 60 as a radiation source. A CO 60 emitter was placed in the middle of the field and plants grew around it.

Singleton's experiments showed that mutations could be induced more effectively by treating corn plants for a short period of time with a fairly high dose of radiation, provided that the period was radiosensitive. In corn, this period occurs about a week before the panicles bloom, but certainly after meiosis, which is the period of pollen sensitivity. Since pollen is easily damaged during irradiation at the time of meiosis, it is necessary to allow meiosis to complete before plants are placed in the radiation field. For maximum efficiency in inducing mutations, plants should not be grown in a radiation field, but only placed for a short time.

Singleton noted that Swedish breeders used radiation to develop new varieties of barley, wheat and oats. Some mutant barley lines have dense ears and very strong culms. Other lines were taller and earlier maturing than the parents. One line produced more grain and straw than its parents. Some of the new oat lines matured earlier, had better grain and produced larger yields. Some of the new wheat lines were lower growing, higher yielding and resistant to stem rust compared to their parents. With the help of radiation, new varieties of peas, vetches and potatoes were developed.

Genetic methods can be used to control populations and control many harmful insects. A variety of documented genetic techniques can be considered for pest control. There are two reasons for this: the long tradition of insect genetics, in which chromosomal manipulation has become an elegant science, and the long tradition of entomology, which evolved from the need to combat insects that carry disease or compete with humans for food.

Wallace and Dobzhansky described the conditions leading to genetic decline and population extinction. They looked at induced recessive lethal mutations and dominant lethal mutations and formulated the idea that extinction could only be caused by the enormous frequency of dominant lethal mutations.

Reports on the evaluation and use of mutations have been made by Quinby, Gaul, Newbohm, Nelson, MacKay, Caldecott, and North. Future uses were predicted by Smith, Nilan and Konzak and Gregory.

Smith and von Borstel listed genetic mechanisms that can cause population decline and destruction. These include: 1) meiotic drift, inseparably associated with genes for female sterility, 2) conditionally lethal mutations, 3) unstable genetic balance caused by chromosome components, translocations.

Gregory discussed mutation selection. One section of his paper is called “Induced Mutations in Quantitative Traits.” Gregory induced a significant increase in genotypic variation in peanut yield by X-ray irradiation of seeds. He reported the suppressive effect of X-rays on the average yield of peanuts. Similar results were obtained by other researchers for rice, soybeans, barley and wheat.

Gregory suggested that the differences in the mutation spectra produced by different types of irradiation and different chemicals suggested that genotype-imposed mutation limitations could be partially overcome by using a large number of mutagens for which differences in specificity had been shown in lower organisms. He concluded that the only big step forward could not be expected from induced mutations in highly adapted material. Gregory emphasized the need to apply continuous pressure to select for a highly refined species.

The frequency of mutations, magnitude of change, and likelihood of cultivar improvement were considered by Gregory. According to his data, in a polygenic system the numbers of plus and minus mutations are approximately the same; there is a magnitude of the phenotypic effect of mutations that gives “minus” effects, and it is not unidirectional. The frequency of observed changes in the peanut population increases as the magnitude of the changes decreases.

The potential usefulness of mutation selection is controversial. However, the latter is another tool in breeding programs.

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