The number of chromosomes in different animal species. Human chromosomes. Who benefits from being wrong?

​What mutations, besides Down syndrome, threaten us? Is it possible to cross a man with a monkey? And what will happen to our genome in the future? The editor of the portal ANTHROPOGENES.RU talked about chromosomes with a geneticist, head. lab. comparative genomics SB RAS Vladimir Trifonov.

− Can you explain in simple language, what is a chromosome?

− A chromosome is a fragment of the genome of any organism (DNA) in complex with proteins. If in bacteria the entire genome is usually one chromosome, then in complex organisms with a pronounced nucleus (eukaryotes) the genome is usually fragmented, and complexes of long fragments of DNA and protein are clearly visible in a light microscope during cell division. That is why chromosomes as colorable structures (“chroma” - color in Greek) were described back in late XIX century.

− Is there any relationship between the number of chromosomes and the complexity of an organism?

- There is no connection. The Siberian sturgeon has 240 chromosomes, the sterlet has 120, but it is sometimes quite difficult to distinguish these two species from each other based on external characteristics. Female Indian muntjac have 6 chromosomes, males have 7, and their relative, the Siberian roe deer, has more than 70 (or rather, 70 chromosomes of the main set and up to a dozen additional chromosomes). In mammals, the evolution of chromosome breaks and fusions proceeded quite intensively, and now we are seeing the results of this process, when each species often has characteristic features karyotype (set of chromosomes). But, undoubtedly, the general increase in genome size was a necessary step in the evolution of eukaryotes. At the same time, how this genome is distributed into individual fragments does not seem to be very important.

− What are some common misconceptions about chromosomes? People often get confused: genes, chromosomes, DNA...

− Since chromosomal rearrangements do occur frequently, people have concerns about chromosomal abnormalities. It is known that an extra copy of the smallest human chromosome (chromosome 21) leads to a rather serious syndrome (Down syndrome), which has characteristic external and behavioral features. Extra or missing sex chromosomes are also quite common and can have serious consequences. However, geneticists have also described quite a few relatively neutral mutations associated with the appearance of microchromosomes, or additional X and Y chromosomes. I think the stigmatization of this phenomenon is due to the fact that people perceive the concept of normal too narrowly.

− What chromosomal mutations occur in modern man and what do they lead to?

− The most common chromosomal abnormalities are:

− Klinefelter syndrome (XXY men) (1 in 500) – characteristic external signs, certain health problems (anemia, osteoporosis, muscle weakness and sexual dysfunction), sterility. There may be behavioral features. However, many symptoms (except sterility) can be corrected by administering testosterone. Using modern reproductive technologies, it is possible to obtain healthy children from carriers of this syndrome;

− Down syndrome (1 in 1000) – characteristic external signs, delayed cognitive development, short life expectancy, may be fertile;

− trisomy X (XXX women) (1 in 1000) – most often there are no manifestations, fertility;

− XYY syndrome (men) (1 in 1000) – almost no manifestations, but there may be behavioral characteristics and possible reproductive problems;

− Turner syndrome (women with CP) (1 in 1500) – short stature and other developmental features, normal intelligence, sterility;

− balanced translocations (1 in 1000) – depends on the type, in some cases developmental defects and mental retardation may be observed and may affect fertility;

− small additional chromosomes (1 in 2000) – the manifestation depends on the genetic material on the chromosomes and varies from neutral to serious clinical symptoms;

Pericentric inversion of chromosome 9 occurs in 1% of the human population, but this rearrangement is considered a normal variant.

Is the difference in the number of chromosomes an obstacle to crossing? Is there any interesting examples crossing animals with different numbers of chromosomes?

− If the crossing is intraspecific or between closely related species, then the difference in the number of chromosomes may not interfere with crossing, but the descendants may turn out to be sterile. There are a lot of hybrids known between species with different numbers of chromosomes, for example, equines: there are all kinds of hybrids between horses, zebras and donkeys, and the number of chromosomes in all equines is different and, accordingly, hybrids are often sterile. However, this does not exclude the possibility that balanced gametes may be produced by chance.

- What unusual things have been discovered recently in the field of chromosomes?

− Recently, there have been many discoveries regarding the structure, function and evolution of chromosomes. I especially like the work that showed that sex chromosomes were formed completely independently in different groups of animals.

- Still, is it possible to cross a man with a monkey?

- Theoretically, it is possible to obtain such a hybrid. Recently, hybrids of much more evolutionarily distant mammals (white and black rhinoceros, alpaca and camel, and so on) have been obtained. The red wolf in America has long been considered a separate species, but has recently been proven to be a hybrid between a wolf and a coyote. There are a huge number of feline hybrids known.

- And a completely absurd question: is it possible to cross a hamster with a duck?

- Here, most likely, nothing will work out, because too many genetic differences have accumulated over hundreds of millions of years of evolution for the carrier of such a mixed genome to function.

- Is it possible that in the future a person will have fewer or more chromosomes?

- Yes, this is quite possible. It is possible that a pair of acrocentric chromosomes will merge and such a mutation will spread throughout the population.

− What popular science literature do you recommend on the topic of human genetics? What about popular science films?

− Books by biologist Alexander Markov, the three-volume “Human Genetics” by Vogel and Motulsky (though this is not science-pop, but there is good reference data there). Nothing comes to mind from films about human genetics... But Shubin’s “Inner Fish” is an excellent film and book of the same name about the evolution of vertebrates.

Poor ecology, life in constant stress, priority of career over family - all this has a bad effect on a person’s ability to bear healthy offspring. Sadly, about 1% of babies born with serious chromosome abnormalities grow up mentally or physically retarded. In 30% of newborns, deviations in the karyotype lead to the formation of congenital defects. Our article is devoted to the main issues of this topic.

Main carrier hereditary information

As is known, a chromosome is a specific nucleoprotein (consisting of a stable complex of proteins and nucleic acids) structure inside the nucleus of a eukaryotic cell (that is, those living creatures whose cells have a nucleus). Its main function is storage, transmission and implementation genetic information. It is visible under a microscope only during processes such as meiosis (division of a double (diploid) set of chromosome genes during the creation of germ cells) and mycosis (cell division during the development of the organism).

As already mentioned, a chromosome consists of deoxyribonucleic acid (DNA) and proteins (about 63% of its mass) on which its thread is wound. Numerous studies in the field of cytogenetics (the science of chromosomes) have proven that DNA is the main carrier of heredity. It contains information that is subsequently implemented in a new organism. This is a complex of genes responsible for hair and eye color, height, number of fingers, etc. Which genes will be passed on to the child are determined at the moment of conception.

Formation of the chromosome set of a healthy organism

U normal person 23 pairs of chromosomes, each of which is responsible for a specific gene. There are 46 in total (23x2) - how many chromosomes a healthy person has. We get one chromosome from our father, the other is passed on from our mother. The exception is 23 pairs. It is responsible for the gender of a person: female is designated as XX, and male as XY. When the chromosomes are in a pair, this is a diploid set. In germ cells they are separated (haploid set) before being subsequently united during fertilization.

The set of characteristics of chromosomes (both quantitative and qualitative) examined within one cell is called a karyotype by scientists. Violations in it, depending on the nature and severity, lead to the occurrence of various diseases.

Deviations in the karyotype

When classified, all karyotype abnormalities are traditionally divided into two classes: genomic and chromosomal.

With genomic mutations, an increase in the number of the entire set of chromosomes, or the number of chromosomes in one of the pairs, is noted. The first case is called polyploidy, the second - aneuploidy.

Chromosomal abnormalities are rearrangements both within and between chromosomes. Without going into scientific jungle, they can be described as follows: some sections of chromosomes may not be present or may be doubled to the detriment of others; The sequence of genes may be disrupted, or their location may be changed. Disturbances in structure can occur in every human chromosome. Currently, the changes in each of them are described in detail.

Let us take a closer look at the most well-known and widespread genomic diseases.

Down syndrome

It was described back in 1866. For every 700 newborns, as a rule, there is one baby with a similar disease. The essence of the deviation is that a third chromosome is added to the 21st pair. This happens when the reproductive cell of one of the parents has 24 chromosomes (with double 21). A sick child ends up with 47 chromosomes - that's how many chromosomes a Down person has. This pathology is promoted by viral infections or ionizing radiation suffered by parents, as well as diabetes.

Children with Down syndrome are mentally retarded. Manifestations of the disease are visible even in appearance: too large a tongue, large ears irregular shape, skin fold on the eyelid and wide bridge of the nose, whitish spots in the eyes. Such people live on average forty years, because, among other things, they are susceptible to heart disease, problems with the intestines and stomach, and undeveloped genitals (although women may be capable of childbearing).

The risk of having a sick child is higher, the older parents. Currently, there are technologies that make it possible to recognize a chromosomal disorder at an early stage of pregnancy. Older couples need to undergo a similar test. It will not hurt young parents if one of them has had Down syndrome in their family. The mosaic form of the disease (the karyotype of some cells is damaged) is formed already at the embryonic stage and does not depend on the age of the parents.

Patau syndrome

This disorder is trisomy of the thirteenth chromosome. It occurs much less frequently than the previous syndrome we described (1 in 6000). It occurs when an extra chromosome is attached, as well as when the structure of chromosomes is disrupted and their parts are redistributed.

Patau syndrome is diagnosed by three symptoms: microphthalmos (reduced eye size), polydactyly (more fingers), cleft lip and palate.

The infant mortality rate for this disease is about 70%. Most of them do not live to be 3 years old. Individuals susceptible to this syndrome most often have heart and/or brain defects, problems with other internal organs(kidneys, spleen, etc.).

Edwards syndrome

Most babies with 3 eighteenth chromosomes die soon after birth. They have pronounced malnutrition (digestive problems that prevent the child from gaining weight). The eyes are set wide and the ears are low. Heart defects are often observed.

Conclusions

To prevent the birth of a sick child, it is advisable to undergo special examinations. The test is mandatory for women giving birth after 35 years of age; parents whose relatives were exposed to similar diseases; patients with thyroid problems; women who have had miscarriages.

Genetics is a science that studies the patterns of heredity and variability of all living beings. It is this science that gives us knowledge about the number of chromosomes in different types organisms, the size of chromosomes, the location of genes on them, and how genes are inherited. Genetics also studies mutations that occur during the formation of new cells.

Chromosome set

Every living organism (the only exception is bacteria) has chromosomes. They are located in every cell of the body in a certain amount. In all somatic cells, chromosomes are repeated twice, three times, or more times, depending on the type of animal or variety of plant organism. In germ cells, the chromosome set is haploid, that is, single. This is necessary so that when two germ cells merge, the correct set of genes for the body is restored. However, the haploid set of chromosomes also contains genes responsible for the organization of the entire organism. Some of them may not appear in the offspring if the second reproductive cell contains more strong signs.

How many chromosomes does a cat have?

You will find the answer to this question in this section. Each type of organism, plant or animal, contains a specific set of chromosomes. The chromosomes of one type of creature have a certain length of the DNA molecule, a certain set of genes. Each such structure has its own size.

And dogs - our pets? A dog has 78 chromosomes. Knowing this number, is it possible to guess how many chromosomes a cat has? It's impossible to guess. Because there is no relationship between the number of chromosomes and the complexity of the organization of the animal. How many chromosomes does a cat have? There are 38 of them.

Chromosome size differences

The DNA molecule, with the same number of genes located on it, can have different lengths in different species.

Moreover, the chromosomes themselves have different sizes. One information structure can accommodate a long or very short DNA molecule. However, chromosomes are never too small. This is due to the fact that when daughter structures diverge, a certain weight of the substance is required, otherwise the divergence itself will not occur.

Number of chromosomes in different animals

As mentioned above, there is no relationship between the number of chromosomes and the complexity of the organization of the animal, because these structures have different sizes.

The number of chromosomes a cat has is the same number of other cats: tiger, jaguar, leopard, puma and other representatives of this family. Many canids have 78 chromosomes. The same amount for domestic chicken. The domestic horse has 64, and the Przewalski's horse has 76.

Humans have 46 chromosomes. Gorillas and chimpanzees have 48, and macaques have 42.

The frog has 26 chromosomes. There are only 16 of them in the somatic cell of a pigeon. And in a hedgehog - 96. In a cow - 120. In a lamprey - 174.

Next, we present data on the number of chromosomes in the cells of some invertebrate animals. The ant, like the roundworm, has only 2 chromosomes in each somatic cell. A bee has 16 of them. A butterfly has 380 such structures in its cell, and radiolarians have about 1,600.

Data from animals show varying numbers of chromosomes. It should be added that Drosophila, which geneticists use during genetic experiments, has 8 chromosomes in somatic cells.

Number of chromosomes in different plants

Flora is also extremely diverse in the number of these structures. Thus, peas and clover each have 14 chromosomes. Onion - 16. Birch - 84. Horsetail - 216, and fern - about 1200.

Differences between males and females

Males and females differ at the genetic level in just one chromosome. In females this structure looks like the Russian letter “X”, and in males it looks like a “Y”. In some animal species, females have a “Y” chromosome and males have an “X”.

Traits located on such non-homologous chromosomes are inherited from father to son and from mother to daughter. The information that is fixed on the “Y” chromosome cannot pass on to the girl, because a person who has this structure is necessarily male.

The same applies to animals: if we see a calico cat, we can definitely say that this is a female.

Because only the X chromosome, which belongs to females, contains the corresponding gene. This structure is the 19th in the haploid set, that is, in germ cells, where the number of chromosomes is always two times less than in somatic ones.

The work of breeders

Knowing the structure of the apparatus that stores information about the body, as well as the laws of inheritance of genes and the characteristics of their manifestation, breeders develop new varieties of plants.

Wild wheat often has a diploid set of chromosomes. There are not many wild representatives that are tetraploid. Cultivated varieties more often contain tetraploid and even hexaploid sets of structures in their somatic cells. This improves yield, weather resistance, and grain quality.

Genetics is an interesting science. The structure of the apparatus, which contains information about the structure of the entire organism, is similar in all living beings. However, each type of creature has its own genetic characteristics. One of the characteristics of a species is the number of chromosomes. Organisms of the same species always have a certain constant number of them.

Sometimes they give us amazing surprises. For example, do you know what chromosomes are and how they affect?

We propose to look into this issue in order to dot the i’s once and for all.

Looking at family photographs, you may have probably noticed that members of the same family resemble each other: children look like parents, parents look like grandparents. This similarity is passed on from generation to generation through amazing mechanisms.

All living organisms, from single-celled organisms to African elephants, contain chromosomes in the cell nucleus - thin, long threads that can only be seen with an electron microscope.

Chromosomes (ancient Greek χρῶμα - color and σῶμα - body) are nucleoprotein structures in the cell nucleus, in which most of the hereditary information (genes) is concentrated. They are designed to store this information, implement it and transmit it.

How many chromosomes does a person have

At the end of the 19th century, scientists discovered that the number of chromosomes in different species is not the same.

For example, peas have 14 chromosomes, y have 42, and in humans – 46 (that is, 23 pairs). Hence the temptation arises to conclude that the more there are, the more complex the creature that possesses them. However, in reality this is absolutely not the case.

Of the 23 pairs of human chromosomes, 22 pairs are autosomes and one pair are gonosomes (sex chromosomes). The sexes have morphological and structural (gene composition) differences.

In a female organism, a pair of gonosomes contains two X chromosomes (XX-pair), and in a male organism, one X-chromosome and one Y-chromosome (XY-pair).

The gender of the unborn child depends on the composition of the chromosomes of the twenty-third pair (XX or XY). This is determined by fertilization and the fusion of the female and male reproductive cells.

This fact may seem strange, but in terms of the number of chromosomes, humans are inferior to many animals. For example, some unfortunate goat has 60 chromosomes, and a snail has 80.

Chromosomes consist of a protein and a DNA (deoxyribonucleic acid) molecule, similar to a double helix. Each cell contains about 2 meters of DNA, and in total there are about 100 billion km of DNA in the cells of our body.

An interesting fact is that if there is an extra chromosome or if at least one of the 46 is missing, a person experiences a mutation and serious developmental abnormalities (Down's disease, etc.).

From school textbooks In biology, everyone has become familiar with the term chromosome. The concept was proposed by Waldeyer in 1888. It literally translates as painted body. The first object of research was the fruit fly.

General information about animal chromosomes

A chromosome is a structure in the cell nucleus that stores hereditary information. They are formed from a DNA molecule that contains many genes. In other words, a chromosome is a DNA molecule. Its amount varies among different animals. So, for example, a cat has 38, and a cow has 120. Interestingly, earthworms and ants have the smallest numbers. Their number is two chromosomes, and the male of the latter has one.

In higher animals, as well as in humans, the last pair is represented by XY sex chromosomes in males and XX in females. It should be noted that the number of these molecules is constant for all animals, but their number differs in each species. For example, we can consider the content of chromosomes in some organisms: chimpanzees have 48, crayfish-196, for a wolf - 78, for a hare - 48. This is due to the different level of organization of a particular animal.

Note! Chromosomes are always arranged in pairs. Geneticists claim that these molecules are the elusive and invisible carriers of heredity. Each chromosome contains many genes. Some believe that the more of these molecules, the more developed the animal, and the more complex its body is. In this case, a person should have not 46 chromosomes, but more than any other animal.

How many chromosomes do different animals have?

You need to pay attention! In monkeys, the number of chromosomes is close to that of humans. But the results are different for each species. So, different monkeys have the following number of chromosomes:

• Lemurs have 44-46 DNA molecules in their arsenal;
• Chimpanzees – 48;
• Baboons – 42,
• Monkeys – 54;
• Gibbons – 44;
• Gorillas – 48;
• Orangutan – 48;
• Macaques - 42.

The canine family (carnivorous mammals) has more chromosomes than monkeys.

• So, the wolf has 78,
• the coyote has 78,
• the small fox has 76,
• but the ordinary one has 34.
• The predatory animals lion and tiger have 38 chromosomes.
• The cat's pet has 38, while his dog opponent has almost twice as many - 78.

In mammals that have economic importance, the number of these molecules is as follows:

• rabbit – 44,
• cow – 60,
• horse – 64,
• pig – 38.

Educational! Hamsters have the largest chromosome sets among animals. They have 92 in their arsenal. Also in this row are hedgehogs. They have 88-90 chromosomes. And kangaroos have the smallest amount of these molecules. Their number is 12. A very interesting fact is that the mammoth has 58 chromosomes. Samples were taken from frozen tissue.

For greater clarity and convenience, data from other animals will be presented in the summary.

Name of animal and number of chromosomes:

Number of chromosomes in different animal species

As you can see, every animal has different amounts chromosomes. Even among representatives of the same family, indicators differ. We can look at the example of primates:

• the gorilla has 48,
• the macaque has 42, and the marmoset has 54 chromosomes.

Why this is so remains a mystery.

How many chromosomes do plants have?

Plant name and number of chromosomes:

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