Gene mutations: causes, examples, classification. Gene mutations

Mutations at the gene level are molecular structural changes in DNA that are not visible in a light microscope. These include any transformation of deoxyribonucleic acid, regardless of their effect on viability and localization. Some types of gene mutations have no effect on the function or structure of the corresponding polypeptide (protein). However, most of these transformations provoke the synthesis of a defective compound that has lost the ability to perform its tasks. Next, we will consider gene and chromosomal mutations in more detail.

Characteristics of transformations

The most common pathologies that provoke human gene mutations are neurofibromatosis, adrenogenital syndrome, cystic fibrosis, and phenylketonuria. This list can also include hemochromatosis, Duchenne-Becker myopathies and others. These are not all examples of gene mutations. Their clinical signs are usually metabolic disorders (metabolic process). Gene mutations may include:

Substitution in a base codon. This phenomenon is called a missense mutation. In this case, a nucleotide is replaced in the coding part, which, in turn, leads to a change in amino acid in the protein.
Changing a codon in such a way that the reading of information is suspended. This process is called nonsense mutation. When a nucleotide is replaced in this case, a stop codon is formed and translation is terminated.
Reading impairment, frame shift. This process is called "frameshifting". When DNA undergoes a molecular change, triplets are transformed during translation of the polypeptide chain.

Classification

According to the type of molecular transformation, the following gene mutations exist:

Duplication. In this case, a repeated duplication or doubling of a DNA fragment occurs from 1 nucleotide to genes.
Deletion. In this case, there is a loss of a DNA fragment from the nucleotide to the gene.
Inversion. In this case, a rotation of 180 degrees is noted. section of DNA. Its size can be either two nucleotides or an entire fragment consisting of several genes.
Insertion. In this case, DNA sections are inserted from the nucleotide to the gene.

Molecular transformations involving from 1 to several units are considered as point changes.

Distinctive features

Gene mutations have a number of features. First of all, it should be noted their ability to be inherited. In addition, mutations can provoke a transformation of genetic information. Some of the changes can be classified as so-called neutral. Such gene mutations do not provoke any disturbances in the phenotype. Thus, due to the innateness of the code, the same amino acid can be encoded by two triplets that differ only in 1 base. At the same time, a certain gene can mutate (transform) into several different states. It is these kinds of changes that provoke most hereditary pathologies. If we give examples of gene mutations, we can turn to blood groups. Thus, the element that controls their AB0 systems has three alleles: B, A and 0. Their combination determines blood groups. Belonging to the AB0 system, it is considered a classic manifestation of the transformation of normal characteristics in humans.

Genomic transformations

These transformations have their own classification. The category of genomic mutations includes changes in the ploidy of structurally unchanged chromosomes and aneuploidy. Such transformations are determined by special methods. Aneuploidy is a change (increase - trisomy, decrease - monosomy) in the number of chromosomes of the diploid set, which is not a multiple of the haploid one. When the number increases by a multiple, we speak of polyploidy. These and most aneuploidies in humans are considered lethal changes. Among the most common genomic mutations are:

Monosomy. In this case, only one of the 2 homologous chromosomes is present. Against the background of such a transformation, healthy embryonic development is impossible for any of the autosomes. The only thing compatible with life is monosomy on the X chromosome. It provokes Shereshevsky-Turner syndrome.
Trisomy. In this case, three homologous elements are detected in the karyotype. Examples of such gene mutations: Down syndrome, Edwards syndrome, Patau syndrome.

Provoking factor

The reason why aneuploidy develops is considered to be non-disjunction of chromosomes during the process of cell division against the background of the formation of germ cells or the loss of elements due to anaphase lag, while when moving towards the pole, a homologous link may lag behind a non-homologous one. The concept of "nondisjunction" indicates the absence of separation of chromatids or chromosomes in mitosis or meiosis. This disorder can lead to mosaicism. In this case, one cell line will be normal and the other will be monosomic.

Nondisjunction in meiosis

This phenomenon is considered the most common. Those chromosomes that should normally divide during meiosis remain connected. In anaphase they move to one cell pole. As a result, 2 gametes are formed. One of them has an extra chromosome, and the other is missing an element. In the process of fertilization of a normal cell with an extra link, trisomy develops; gametes with a missing component develop monosomy. When a monosomic zygote is formed for some autosomal element, development stops at the initial stages.

Chromosomal mutations

These transformations represent structural changes of elements. Typically, they are visualized using a light microscope. Chromosome mutations typically involve tens to hundreds of genes. This provokes changes in the normal diploid set. Typically, such aberrations do not cause sequence transformation in DNA. However, when the number of gene copies changes, a genetic imbalance develops due to a lack or excess of material. There are two broad categories of these transformations. In particular, intra- and interchromosomal mutations are distinguished.

Environmental influence

Humans evolved as groups of isolated populations. They lived for quite a long time in the same environmental conditions. We are talking, in particular, about the nature of nutrition, climatic and geographical characteristics, cultural traditions, pathogens, etc. All this led to the consolidation of combinations of alleles specific to each population, which were most appropriate for living conditions. However, due to the intensive expansion of the area, migrations, and resettlement, situations began to arise when useful combinations of certain genes that were in one environment in another ceased to ensure the normal functioning of a number of body systems. In this regard, part of the hereditary variability is caused by an unfavorable complex of non-pathological elements. Thus, the cause of gene mutations in this case is changes in the external environment and living conditions. This, in turn, became the basis for the development of a number of hereditary diseases.

Natural selection

Over time, evolution took place in more specific species. This also contributed to the expansion of ancestral diversity. Thus, those signs that could disappear in animals were preserved, and, conversely, what remained in animals was swept away. In the course of natural selection, people also acquired undesirable traits that were directly related to diseases. For example, during human development, genes appeared that can determine sensitivity to polio or diphtheria toxin. Having become Homo sapiens, the human species in some way “paid for its intelligence” with the accumulation of pathological transformations. This provision is considered the basis of one of the basic concepts of the doctrine of gene mutations.

Gene mutations are changes in the structure of one gene. This is a change in the nucleotide sequence: deletion, insertion, substitution, etc. For example, replacing a with t. Causes - violations during DNA doubling (replication)

Gene mutations are molecular changes in DNA structure that are not visible in a light microscope. Gene mutations include any changes in the molecular structure of DNA, regardless of their location and effect on viability. Some mutations have no effect on the structure or function of the corresponding protein. Another (large) part of gene mutations leads to the synthesis of a defective protein that is unable to perform its inherent function. It is gene mutations that determine the development of most hereditary forms of pathology.

The most common monogenic diseases in humans are: cystic fibrosis, hemochromatosis, adrenogenital syndrome, phenylketonuria, neurofibromatosis, Duchenne-Becker myopathies and a number of other diseases. Clinically, they manifest themselves as signs of metabolic disorders (metabolism) in the body. The mutation may be:

1) in replacing a base in a codon, this is the so-called missense mutation(from English, mis - false, incorrect + lat. sensus - meaning) - replacement of a nucleotide in the coding part of a gene, leading to replacement of an amino acid in a polypeptide;

2) in such a change in codons that will lead to a stop in reading information, this is the so-called nonsense mutation(from Latin non - no + sensus - meaning) - replacement of a nucleotide in the coding part of a gene leads to the formation of a terminator codon (stop codon) and cessation of translation;

3) a violation of information reading, a shift in the reading frame, called frameshift(from the English frame - frame + shift: - shift, movement), when molecular changes in DNA lead to changes in triplets during translation of the polypeptide chain.

Other types of gene mutations are also known. Based on the type of molecular changes, there are:

division(from Latin deletio - destruction), when a DNA segment ranging in size from one nucleotide to a gene is lost;

duplications(from Latin duplicatio - doubling), i.e. duplication or reduplication of a DNA segment from one nucleotide to entire genes;

inversions(from Latin inversio - turning over), i.e. a 180° rotation of a DNA segment ranging in size from two nucleotides to a fragment including several genes;

insertions(from Latin insertio - attachment), i.e. insertion of DNA fragments ranging in size from one nucleotide to an entire gene.

Molecular changes affecting one to several nucleotides are considered a point mutation.

The fundamental and distinctive feature of a gene mutation is that it 1) leads to a change in genetic information, 2) can be transmitted from generation to generation.

A certain part of gene mutations can be classified as neutral mutations, since they do not lead to any changes in the phenotype. For example, due to the degeneracy of the genetic code, the same amino acid can be encoded by two triplets that differ in only one base. On the other hand, the same gene can change (mutate) into several different states.

For example, the gene that controls the blood group of the AB0 system. has three alleles: 0, A and B, the combinations of which determine 4 blood groups. The ABO blood group is a classic example of genetic variation in normal human characteristics.

It is gene mutations that determine the development of most hereditary forms of pathology. Diseases caused by such mutations are called genetic, or monogenic, diseases, i.e., diseases whose development is determined by a mutation of one gene.

Genomic and chromosomal mutations

Genomic and chromosomal mutations are the causes of chromosomal diseases. Genomic mutations include aneuploidies and changes in the ploidy of structurally unchanged chromosomes. Detected by cytogenetic methods.

Aneuploidy- a change (decrease - monosomy, increase - trisomy) in the number of chromosomes in a diploid set, not a multiple of the haploid set (2n + 1, 2n - 1, etc.).

Polyploidy- an increase in the number of sets of chromosomes, a multiple of the haploid one (3n, 4n, 5n, etc.).

In humans, polyploidy, as well as most aneuploidy, are lethal mutations.

The most common genomic mutations include:

trisomy- the presence of three homologous chromosomes in the karyotype (for example, on the 21st pair in Down syndrome, on the 18th pair in Edwards syndrome, on the 13th pair in Patau syndrome; on sex chromosomes: XXX, XXY, XYY);

monosomy- the presence of only one of two homologous chromosomes. With monosomy for any of the autosomes, normal development of the embryo is impossible. The only monosomy in humans that is compatible with life, monosomy on the X chromosome, leads to Shereshevsky-Turner syndrome (45, X0).

The reason leading to aneuploidy is the nondisjunction of chromosomes during cell division during the formation of germ cells or the loss of chromosomes as a result of anaphase lag, when during movement to the pole one of the homologous chromosomes may lag behind all other nonhomologous chromosomes. The term "nondisjunction" means the absence of separation of chromosomes or chromatids in meiosis or mitosis. Loss of chromosomes can lead to mosaicism, in which there is one uploid(normal) cell line, and the other monosomic.

Chromosome nondisjunction most often occurs during meiosis. Chromosomes that would normally divide during meiosis remain joined together and move to one pole of the cell during anaphase. Thus, two gametes arise, one of which has an additional chromosome, and the other does not have this chromosome. When a gamete with a normal set of chromosomes is fertilized by a gamete with an extra chromosome, trisomy occurs (i.e., there are three homologous chromosomes in the cell); when a gamete without one chromosome is fertilized, a zygote with monosomy occurs. If a monosomal zygote is formed on any autosomal (non-sex) chromosome, then the development of the organism stops at the earliest stages of development.

Chromosomal mutations- These are structural changes in individual chromosomes, usually visible under a light microscope. A chromosomal mutation involves a large number (from tens to several hundreds) of genes, which leads to a change in the normal diploid set. Although chromosomal aberrations generally do not change the DNA sequence of specific genes, changes in the copy number of genes in the genome lead to genetic imbalance due to a lack or excess of genetic material. There are two large groups of chromosomal mutations: intrachromosomal and interchromosomal.

Intrachromosomal mutations are aberrations within one chromosome. These include:

—deletions(from Latin deletio - destruction) - loss of one of the sections of the chromosome, internal or terminal. This can cause disruption of embryogenesis and the formation of multiple developmental anomalies (for example, division in the region of the short arm of the 5th chromosome, designated as 5p-, leads to underdevelopment of the larynx, heart defects, and mental retardation). This symptom complex is known as the “cry of the cat” syndrome, since in sick children, due to an abnormality of the larynx, the crying resembles a cat’s meow;

—inversions(from Latin inversio - inversion). As a result of two chromosome break points, the resulting fragment is inserted into its original place after a 180° rotation. As a result, only the order of the genes is disrupted;

— duplications(from Latin duplicatio - doubling) - doubling (or multiplication) of any part of a chromosome (for example, trisomy on one of the short arms of the 9th chromosome causes multiple defects, including microcephaly, delayed physical, mental and intellectual development).

Patterns of the most common chromosomal aberrations:
Division: 1 - terminal; 2 - interstitial. Inversions: 1 - pericentric (with capture of the centromere); 2 - paracentric (within one chromosome arm)

Interchromosomal mutations, or rearrangement mutations- exchange of fragments between non-homologous chromosomes. Such mutations are called translocations (from the Latin tgans - for, through + locus - place). This:

Reciprocal translocation, when two chromosomes exchange their fragments;

Non-reciprocal translocation, when a fragment of one chromosome is transported to another;

- “centric” fusion (Robertsonian translocation) - the connection of two acrocentric chromosomes in the region of their centromeres with the loss of short arms.

When chromatids break transversely through centromeres, “sister” chromatids become “mirror” arms of two different chromosomes containing the same sets of genes. Such chromosomes are called isochromosomes. Both intrachromosomal (deletions, inversions and duplications) and interchromosomal (translocations) aberrations and isochromosomes are associated with physical changes in chromosome structure, including mechanical breaks.

Hereditary pathology as a result of hereditary variability

The presence of common species characteristics allows us to unite all people on earth into a single species, Homo sapiens. Nevertheless, we easily, with one glance, single out the face of a person we know in a crowd of strangers. The extreme diversity of people - both within groups (for example, diversity within an ethnic group) and between groups - is due to their genetic differences. It is currently believed that all intraspecific variation is due to different genotypes arising and maintained by natural selection.

It is known that the haploid human genome contains 3.3x10 9 pairs of nucleotide residues, which theoretically allows for up to 6-10 million genes. At the same time, modern research data indicate that the human genome contains approximately 30-40 thousand genes. About a third of all genes have more than one allele, that is, they are polymorphic.

The concept of hereditary polymorphism was formulated by E. Ford in 1940 to explain the existence in a population of two or more distinct forms when the frequency of the rarest of them cannot be explained by mutational events alone. Since gene mutation is a rare event (1x10 6), the frequency of the mutant allele, which is more than 1%, can only be explained by its gradual accumulation in the population due to the selective advantages of carriers of this mutation.

The multiplicity of segregating loci, the multiplicity of alleles in each of them, along with the phenomenon of recombination, creates inexhaustible human genetic diversity. Calculations show that in the entire history of mankind there has not been, is not, and will not occur in the foreseeable future, genetic repetition, i.e. Every born person is a unique phenomenon in the Universe. The uniqueness of the genetic constitution largely determines the characteristics of the development of the disease in each individual person.

Humanity has evolved as groups of isolated populations living for a long time under the same environmental conditions, including climatic and geographic characteristics, dietary patterns, pathogens, cultural traditions, etc. This led to the consolidation in the population of combinations of normal alleles specific for each of them, most adequate to environmental conditions. Due to the gradual expansion of the habitat, intensive migrations, and resettlement of peoples, situations arise when combinations of specific normal genes that are useful in certain conditions do not ensure the optimal functioning of certain body systems in other conditions. This leads to the fact that part of the hereditary variability, caused by an unfavorable combination of non-pathological human genes, becomes the basis for the development of so-called diseases with a hereditary predisposition.

In addition, in humans as a social being, natural selection proceeded over time in increasingly specific forms, which also expanded hereditary diversity. What could be discarded by the animals was preserved, or, conversely, what the animals retained was lost. Thus, fully meeting the needs for vitamin C led in the process of evolution to the loss of the L-gulonodactone oxidase gene, which catalyzes the synthesis of ascorbic acid. In the process of evolution, humanity also acquired undesirable characteristics that are directly related to pathology. For example, in the process of evolution, humans have acquired genes that determine sensitivity to diphtheria toxin or to the polio virus.

Thus, in humans, like in any other biological species, there is no sharp line between hereditary variability leading to normal variations in characteristics and hereditary variability causing the occurrence of hereditary diseases. Man, having become the biological species Homo sapiens, seemed to pay for the “reasonableness” of his species by accumulating pathological mutations. This position underlies one of the main concepts of medical genetics about the evolutionary accumulation of pathological mutations in human populations.

Hereditary variability of human populations, both maintained and reduced by natural selection, forms the so-called genetic load.

Some pathological mutations can persist and spread in populations for a historically long time, causing the so-called segregation genetic load; other pathological mutations arise in each generation as a result of new changes in the hereditary structure, creating a mutational load.

The negative effect of genetic load is manifested by increased mortality (death of gametes, zygotes, embryos and children), decreased fertility (reduced reproduction of offspring), decreased life expectancy, social disadaptation and disability, and also causes an increased need for medical care.

The English geneticist J. Hoddane was the first to draw the attention of researchers to the existence of genetic load, although the term itself was proposed by G. Meller back in the late 40s. The meaning of the concept of “genetic load” is associated with the high degree of genetic variability necessary for a biological species in order to be able to adapt to changing environmental conditions.

We are used to saying that each person is unique, implying a deep inner world, but sometimes people are born who are distinguished from the general mass not only by their character, but also by their appearance. We will tell you about the 10 most terrible genetic mutations that occur in isolated cases in people.

1. Ectrodactyly

One of the congenital malformations in which the fingers and/or feet are completely absent or underdeveloped. Caused by a malfunction of the seventh chromosome. Often the disease is accompanied by a complete lack of hearing.

2. Hypertrichosis

During the Middle Ages, people with a similar gene defect were called werewolves or apes. This disease is characterized by excessive hair growth throughout the body, including the face and ears. The first case of hypertrichosis was recorded in the 16th century.

3. Fibrodysplasia ossificans progressiva (FOP)

A rare genetic disease in which the body begins to form new bones (ossifications) in the wrong places - inside muscles, ligaments, tendons and other connective tissues. Any injury can lead to their formation: bruise, cut, fracture, intramuscular injection or surgery. Because of this, it is impossible to remove ossifications: after surgery, the bone can only grow stronger. Physiologically, ossifications are no different from ordinary bones and can withstand significant loads, but they are not located where they should be.

4. Progressive lipodystrophy

People suffering from this unusual condition appear much older than their age, which is why it is sometimes called “reverse Benjamin Button syndrome.” Due to an inherited genetic mutation, and sometimes as a result of the use of certain medications, autoimmune mechanisms in the body are disrupted, which leads to rapid loss of subcutaneous fat reserves. Most often, the fatty tissue of the face, neck, upper limbs and torso is affected, resulting in wrinkles and folds. So far, only 200 cases of progressive lipodystrophy have been confirmed, and it mainly develops in women. In treatment, doctors use insulin, facelifts and collagen injections, but this only gives a temporary effect.

5. Yuner Tang syndrome

Yuner Tan syndrome (UTS) is characterized primarily by the fact that people suffering from it walk on all fours. It was discovered by Turkish biologist Yuner Tan after studying five members of the Ulas family in rural Turkey. Most often, people with SUT use primitive speech and have congenital brain deficiency. In 2006, a documentary film was made about the Ulas family called “The Family Walking on All Fours.” Tan describes it this way: "The genetic nature of the syndrome suggests a reversal of human evolution, most likely caused by a genetic mutation, reversing the transition from quadropedalism (walking on four limbs) to bipedalism (walking on two limbs). In this case, the syndrome corresponds to the intermittent theory balance.

6. Progeria

Occurs in one child out of 8,000,000. This disease is characterized by irreversible changes in the skin and internal organs caused by premature aging of the body. The average life expectancy of people with this disease is 13 years. There is only one known case in which the patient reached the age of forty-five years. The case was recorded in Japan.

7. Epidermodysplasia verruciformis

One of the rarest gene failures. It makes its owners very sensitive to the widespread human papillomavirus (HPV). In such people, the infection causes the growth of numerous skin growths that resemble wood in density. The disease became widely known in 2007 after a video of 34-year-old Indonesian Dede Kosvara appeared on the Internet. In 2008, a man underwent a complex operation to remove six kilograms of growths from his head, arms, legs and torso. New skin was transplanted onto the operated parts of the body. But, unfortunately, after some time the growths appeared again.

8. Proteus syndrome

Proteus syndrome causes rapid and disproportionate growth of bones and skin, caused by a mutation in the AKT1 gene. It is this gene that is responsible for proper cell growth. Due to a malfunction in its operation, some cells rapidly grow and divide, while others continue to grow at a normal pace. This results in an abnormal appearance. The disease does not appear immediately after birth, but only at six months of age.

9. Trimethylaminuria

It is one of the rarest genetic diseases. There are not even statistics on its distribution. In those suffering from this disease, trimethylamine accumulates in the body. This substance with a sharp unpleasant odor, reminiscent of the smell of rotten fish and eggs, is secreted along with sweat and creates an unpleasant fetid amber around the patient. Naturally, people with such a genetic malfunction avoid crowded places and are prone to depression.

10. Xeroderma pigmentosum

This hereditary skin disease manifests itself in a person's increased sensitivity to ultraviolet rays. It occurs due to mutations in proteins responsible for correcting DNA damage that occurs when exposed to ultraviolet radiation. The first symptoms usually appear in early childhood (up to 3 years): when the child is in the sun, he develops serious burns after just a few minutes of exposure to sunlight. The disease is also characterized by the appearance of freckles, dry skin and uneven discoloration of the skin. According to statistics, people with xeroderma pigmentosum are more at risk of developing cancer than others - in the absence of proper preventive measures, approximately half of children suffering from xeroderma develop some kind of cancer by the age of ten. There are eight types of this disease, varying in severity and symptoms. According to European and American doctors, the disease occurs in approximately four people out of a million.

We will tell you about the 10 most terrible genetic mutations that occur in isolated cases in people.

1. Ectrodactyly

2. Hypertrichosis

3. Fibrodysplasia ossificans progressiva (FOP)

4. Progressive lipodystrophy

5. Yuner Tang syndrome

6. Progeria

7. Epidermodysplasia verruciformis

8. Proteus syndrome

9. Trimethylaminuria

10. Xeroderma pigmentosum

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Unfortunately, among us there are people who stand out from the crowd with something that, at first glance, is repulsive and scary. These are genetic mutations that make a person different, not like everyone else. We can’t help but talk about the most terrible mutations that people can have...

1. Ectrodactyly

A congenital malformation caused by a malfunction of the seventh chromosome. Manifests itself in the absence or underdevelopment of fingers and/or feet. Often accompanied by a complete lack of hearing.

2. Hypertrichosis

This disease involves excessive hair growth throughout the body, including the face. The first case of hypertrichosis was recorded in the 16th century. In ancient times, such people were called werewolves or apes.

3. Fibrodysplasia ossificans progressiva (FOP)

A rare disease in which the body forms new bones (ossifications) in the wrong places - inside muscles, ligaments, tendons and other connective tissues. Their formation can be triggered by injury - a bruise, a cut, a fracture, even an intramuscular injection or surgery. It is impossible to remove ossifications - after removal the bone may grow even more...

4. Progressive lipodystrophy

“Reverse Benjamin Button syndrome” is also called this disease, because people suffering from it look much older than their real age. Due to an inherited genetic mutation or the use of certain drugs, autoimmune mechanisms are disrupted, which leads to rapid loss of subcutaneous fat reserves and the appearance of wrinkles and folds. So far, only 200 cases of lipodystrophy have been recorded, mainly in women. The disease has no cure; doctors do collagen injections and facelifts, but this only gives a temporary effect.

5. Yuner Tang syndrome

People suffering from this syndrome walk on all fours, use primitive speech and have congenital brain failure. The disease was discovered by Turkish biologist Yuner Tan after studying five members of the Ulas family in rural Turkey. In 2006, a documentary film was made about them called “The Family Walking on All Fours.” “The genetic nature of the syndrome suggests a reverse step in human evolution, most likely caused by a genetic mutation, the reverse process of transition from quadropedalism (walking on four limbs) to bipedalism (walking on two). In this case, the syndrome corresponds to the theory of punctuated equilibrium,” the biologist explains his discovery.

6. Progeria

These are irreversible changes in the skin and internal organs caused by premature aging of the body. The disease affects one in 8 million children, and they live an average of 13 years. In Japan, there was only one recorded case where a man with progeria lived to be 45 years old.

7. Epidermodysplasia verruciformis

People with this genetic disorder are very susceptible to the common human papillomavirus (HPV). This causes dense growths on the body that resemble wood. The disease became widely known in 2007, when a documentary about 34-year-old Indonesian Ded Koswar was released. In 2008, the man underwent surgery to transplant “clean” skin onto his head, arms, legs and torso. But, unfortunately, soon the growths began to appear again...

8. Proteus syndrome

The syndrome is caused by a mutation in the AKT1 gene and is characterized by rapid and disproportionate growth of bones and skin. The AKT1 gene is responsible for proper cell growth, and when a failure occurs, some cells grow and divide rapidly, while others continue to grow at a normal pace. This is how a person begins to look abnormal. The disease appears only six months after the birth of the child.

9. Trimethylaminuria

One of the rarest genetic diseases. In a person with this disorder, trimethylamine accumulates in the body - a substance with a strong unpleasant odor, reminiscent of the smell of rotten fish and eggs. It is excreted along with sweat and creates an unpleasant, fetid cloud around the patient. People suffering from trimethylaminuria are prone to depression and avoid crowded places.

10. Xeroderma pigmentosum

Manifested by increased sensitivity of the skin to ultraviolet rays. The disease occurs due to mutations in proteins responsible for correcting DNA damage that occurs when exposed to ultraviolet radiation. Freckles, dry skin, burns on the body, changes in skin color, and the risk of cancer are common symptoms of xeroderma pigmentosum.