What animals have 46 chromosomes. How many chromosomes does a cat have? Genetics provides data on various genomes. The number of chromosomes in different plants

Bad ecology, life in constant stress, the priority of a career over a family - all this has a bad effect on a person's ability to bring healthy offspring. It is regrettable, but about 1% of babies born with serious disorders in the chromosomal set grow up mentally or physically retarded. In 30% of newborns, deviations in the karyotype lead to the formation of congenital malformations. Our article is devoted to the main issues of this topic.

The main carrier of hereditary information

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

As already mentioned, the 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) proved 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, and more. Which of the genes will be passed on to the child is determined at the time of conception.

Formation of the chromosome set of a healthy organism

At normal person 23 pairs of chromosomes, each of which is responsible for a specific gene. There are 46 (23x2) in total - how many chromosomes do healthy person. One chromosome is inherited from our father, the other is inherited from our mother. The exception is 23 pairs. She is responsible for the gender of a person: female is designated as XX, and male as XY. When chromosomes are paired, this is a diploid set. In germ cells, they are separated (haploid set) before the next connection during fertilization.

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

Deviations in the karyotype

All karyotype disorders in the classification 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 disorders are rearrangements, both within chromosomes and between them. Without going into scientific jungle, they can be described as follows: some parts of the chromosomes may not be present or may be doubled to the detriment of others; the order of the genes may be violated, or their location changed. Structural abnormalities can occur in every human chromosome. Currently, the changes in each of them are described in detail.

Let us dwell in more detail on the most well-known and widespread genomic diseases.

Down syndrome

It was described as early as 1866. For every 700 newborns, as a rule, there is one baby with a similar disease. The essence of the deviation is that the third chromosome joins the 21st pair. This happens when there are 24 chromosomes in the germ cell of one of the parents (with a doubled 21). In a sick child, as a result, there are 47 of them - that's how many chromosomes a Down person has. This pathology is promoted by viral infections or ionizing radiation transferred by parents, as well as diabetes.

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

The risk of having a sick child is higher, the older the parents. Currently, there are technologies that allow to recognize a chromosomal disorder on early stage pregnancy. Older couples need to pass a similar test. He will not interfere with young parents, if in the family of one of them there were patients with Down syndrome. The mosaic form of the disease (the karyotype of a part of the cells is damaged) is formed already at the stage of the embryo and does not depend on the age of the parents.

Patau Syndrome

This disorder is a 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 disturbed 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 up to 3 years. Individuals prone 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 shortly after birth. They have pronounced malnutrition (digestion problems that prevent the child from gaining weight). The eyes are set wide, the ears are low. Often there is a heart defect.

conclusions

In order to prevent the birth of a sick child, it is desirable to undergo special examinations. Without fail, the test is shown to women in labor after 35 years; parents whose relatives were susceptible to similar diseases; patients with thyroid problems; women who have had miscarriages.

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

− Can you explain plain language what is a chromosome?

- A chromosome is a fragment of the genome of any organism (DNA) in combination 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 DNA and protein fragments are clearly visible in a light microscope during cell division. That is why chromosomes as staining structures (“chroma” - color in Greek) were described as early as the end of the 19th century.

- Is there any connection between the number of chromosomes and the complexity of the 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 by external signs. Females of the 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 even up to a dozen additional chromosomes). In mammals, the evolution of chromosome breaks and fusions was quite intensive, and now we are seeing the results of this process, when often each species has characteristics karyotype (set of chromosomes). But, undoubtedly, the general increase in the size of the genome was a necessary step in the evolution of eukaryotes. At the same time, how this genome is distributed over individual fragments does not seem to be very important.

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

- Since chromosomal rearrangements really often occur, 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's 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 the norm too narrowly.

What chromosomal mutations are found in modern man and what do they lead to?

- The most common chromosomal abnormalities are:

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

- Down's syndrome (1 per 1000) - characteristic external signs, delayed cognitive development, short life expectancy, may be fertile;

- trisomy X (XXX women) (1 per 1000) - most often there are no manifestations, fertility;

- XYY syndrome (men) (1 in 1000) - almost no manifestations, but there may be behavioral features and reproductive problems are possible;

- Turner's syndrome (women CW) (1 per 1500) - short stature and other developmental features, normal intelligence, sterility;

- balanced translocations (1 per 1000) - depends on the type, in some cases malformations and mental retardation may be observed, may affect fertility;

- small extra chromosomes (1 in 2000) - the manifestation depends on the genetic material on the chromosomes and varies from neutral to severe clinical symptoms;

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

Is the difference in the number of chromosomes an obstacle to crossing? Is there 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 offspring may be sterile. A lot of hybrids are known between species with different numbers of chromosomes, for example, in horses: there are all variants of hybrids between horses, zebras and donkeys, and the number of chromosomes in all horses is different and, accordingly, hybrids are often sterile. However, this does not exclude the possibility that balanced gametes may be formed by chance.

- What was unusual in the field of chromosomes was discovered in Lately?

- Recently, there have been many discoveries regarding the structure, functioning and evolution of chromosomes. I especially like the work that has shown that the sex chromosomes formed in different groups of animals quite independently.

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

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

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

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

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

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

- What popular science literature would you recommend on the topic of human genetics? What about popular science films?

− Books by the biologist Alexander Markov, the three-volume book “Human Genetics” by Vogel and Motulsky (although this is not pop-science, but there is good reference data there). From films about human genetics, nothing comes to mind ... But here " domestic fish» Shubin is an excellent film and a book of the same name about the evolution of vertebrates.

Did Charles Darwin at the end of his life renounce his theory of human evolution? Did ancient people find dinosaurs? Is it true that Russia is the cradle of mankind, and who is the Yeti - is it not one of our ancestors who got lost in the centuries? Although paleoanthropology - the science of human evolution - is experiencing a rapid flowering, the origin of man is still surrounded by many myths. These are both anti-evolutionary theories and legends generated by popular culture, and near-scientific ideas that exist among educated and well-read people. Do you want to know how it was "really"? Alexander Sokolov, Chief Editor portal ANTROPOGENESIS.RU, collected a whole collection of such myths and checked how well-founded they are.

At the level of everyday logic, it is obvious that “a monkey is cooler than a person - it has two whole chromosomes more!”. Thus, “the origin of man from apes is finally refuted” ...

Let us remind our dear readers that chromosomes are the things in which DNA is packaged in our cells. A person has 23 pairs of chromosomes (23 we got from mom and 23 from dad. Total 46). The complete set of chromosomes is called a "karyotype". Each chromosome contains a very large DNA molecule tightly coiled.

It is not the number of chromosomes that matters, but the genes that these chromosomes contain. The same set of genes can be packed into different numbers of chromosomes.

For example, two chromosomes were taken and merged into one. The number of chromosomes has decreased, but the genetic sequence that is contained in them has remained the same. (Imagine that a wall was broken between two neighboring rooms. One large room turned out, but the content - furniture and parquet - is the same ...)

The fusion of chromosomes occurred in our ancestor. That is why we have two fewer chromosomes than chimpanzees, despite the fact that the genes are almost the same.

How do we know about the closeness of human and chimpanzee genes?

In the 1970s, when biologists learned to compare genetic sequences different types, this has been done for humans and chimpanzees. Specialists were in for a shock: “ The difference in the nucleotide sequences of the substance of heredity - DNA - in humans and chimpanzees as a whole was 1.1%,- wrote the famous Soviet primatologist E. P. Fridman in the book "Primates". - ... Frog species or squirrels within the same genus differ from each other 20–30 times more than chimpanzees and humans. It was so surprising that I had to urgently somehow explain the discrepancy between molecular data and what is known at the level of the whole organism.» .

And in 1980 in an authoritative magazine Science University of Minneapolis genetics team published The Striking Resemblance of High-Resolution G-Banded Chromosomes of Man and Chimpanzee.

The researchers used the latest methods of coloring chromosomes at that time (transverse stripes of different thickness and brightness appear on the chromosomes; at the same time, each chromosome differs in its own special set of stripes). It turned out that in humans and chimpanzees, the striation of chromosomes is almost identical! But what about the extra chromosome? And it’s very simple: if we put the 12th and 13th chromosomes of a chimpanzee in one line opposite the second human chromosome, connecting them at the ends, we will see that together they make up the second human.

Later, in 1991, researchers looked at the point of the alleged fusion on the second human chromosome and found there what they were looking for - DNA sequences characteristic of telomeres - the terminal sections of chromosomes. Another proof that there were once two in place of this chromosome!

But how does such a merger take place? Suppose one of our ancestors had two chromosomes combined into one. He got an odd number of chromosomes - 47, while the rest of the non-mutated individuals still have 48! And how did such a mutant then multiply? How can individuals with different numbers of chromosomes interbreed?

It would seem that the number of chromosomes clearly distinguishes between species and is an insurmountable obstacle to hybridization. What was the surprise of the researchers when, studying the karyotypes of various mammals, they began to find a scatter in the number of chromosomes within some species! So, in different populations common shrew this figure can walk from 20 to 33. And the varieties of the musk shrew, as noted in the article by P. M. Borodin, M. B. Rogacheva and S. I. Oda, “differ from each other more than a person from a chimpanzee: animals living in the south of Hindustan and Sri Lanka , have 15 pairs of chromosomes in the karyotype, and all other shrews from Arabia to the islands of Oceania - 20 pairs ... It turned out that the number of chromosomes decreased because five pairs of chromosomes of a typical species merged with each other: 8th with 16th, 9? I am from the 13th, etc.”

Mystery! Let me remind you that during meiosis - cell division, as a result of which sex cells are formed - each chromosome in the cell must connect with its homologue pair. And here, when merged, an unpaired chromosome appears! Where should she go?

It turns out the problem is solved! PM Borodin describes this process, which he personally registered in 29 chromosome punares. Punare are bristly rats native to Brazil. Individuals with 29 chromosomes were obtained by crossing between 30 and 28 chromosome punare belonging to different populations of this rodent.

During meiosis in such hybrids, paired chromosomes successfully found each other. “And the remaining three chromosomes formed a triple: on the one hand, a long chromosome received from a 28 chromosome parent, and on the other, two shorter ones that came from a 30 chromosome parent. In this case, each chromosome stood in its place"

Genetics is a science that studies the laws of heredity and variability of all living beings. It is this science that gives us knowledge about the number of chromosomes in different types of 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.

Chromosomal set

Every living organism (the only exceptions are bacteria) has chromosomes. They are located in every cell of the body in a certain amount. In all somatic cells, chromosomes are repeated twice, thrice, or more times, depending on the type of animal or type 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, even in the haploid set of chromosomes, the genes responsible for the organization of the whole organism are concentrated. Some of them may not appear in offspring if the second sex cell contains stronger features.

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 certain set of chromosomes. The chromosomes of one species of creatures have a certain length of the DNA molecule, a certain set of genes. Each such structure has its own size.

And dogs are 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 are of different sizes. One information structure can contain a long or very short DNA molecule. However, chromosomes are not too small. This is due to the fact that when the daughter structures diverge, a certain weight of the substance is necessary, otherwise the divergence itself will not occur.

The 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 a different size.

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

Humans have 46 chromosomes. The gorilla and chimpanzee have 48, while the macaque has 42.

A frog has 26 chromosomes. In the somatic cell of a pigeon there are only 16 of them. 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 invertebrates. 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 per cell, and radiolarians have about 1600.

Animal data show different numbers of chromosomes. It must be added that Drosophila, which geneticists use in the course of genetic experiments, has 8 chromosomes in somatic cells.

The number of chromosomes in different plants

Vegetable world is also extremely diverse in the number of these structures. So, 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 at the genetic level differ in only one chromosome. In females, this structure looks like the Russian letter "X", and in males it looks like "Y". In some animal species, females have a "Y" chromosome, and males have an "X".

Traits found 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 be transferred to a girl, because a person who has this structure is necessarily male.

The same applies to animals: if we see a tricolor cat, we can say for sure that we have a female in front of us.

Because only the X chromosome, which belongs to females, has 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.

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 features of their manifestation, breeders breed new plant varieties.

Wild wheat often has a diploid set of chromosomes. Not so much wild representatives with a tetraploid set. Cultivated varieties 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 device of the apparatus containing information about the structure of the whole 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. In organisms of the same species, there is always a certain constant amount of them.