The number of chromosomes in different organisms is up to 100. How many chromosomes do different animals have

Do all living organisms have chromosomes? Do all mammalian cells have these structures? How many chromosomes does this or that organism have? Geneticists study such questions. Many similar questions have already been answered. Data on the number, size and shape of chromosomes are increasingly being used in other biological sciences. Particularly in taxonomy.

Chromosomes are information structures

What is a chromosome? If we examine a eukaryotic cell under high magnification, then in the normal state of this “building block” of the organism, we will not see any chromosome-like structures. They are formed only before cell division, and immediately after the end of reproduction, dense structures disappear, as if dissolving. Chromosomes are necessary for the uniform distribution of information material between daughter cells. They are formed by a DNA molecule and proteins that maintain the dense structure of the chromosome.

What is a karyotype

Each chromosome has its own size and shape. One type of organism is characterized by a certain set of chromosomes. Different individuals of the same species always have the same amount of these information structures; these structures have a size and shape characteristic of a particular species.

Thus, a karyotype is the external characteristics of chromosomes and their number in individuals of the same species. Unlike the genome, a karyotype does not include specific characteristics of individuals, but only the appearance of chromosomal structures. Karyotype features help taxonomists correctly distribute living organisms into taxonomic groups.

How many chromosomes do dogs have

Each type of organism has a certain number of chromosomes. This applies to all eukaryotes. Prokaryotes have a circular DNA molecule, which also doubles during cell division and is distributed among daughter cells without the formation of chromosomal structures.

The number of chromosomes varies extremely among different representatives of the animal and plant kingdoms. For example, a person has 46 chromosomes in somatic cells. This is a diploid set. There are 23 structures in human germ cells. How many chromosomes do dogs have? Their number cannot simply be guessed for each organism. The karyotype of a dog consists of 78 chromosomes. How many chromosomes does a wolf have in this case? Here there is a similarity in karyotype. Because all wolves are relatives to each other and to the domestic dog. Almost all wolves also have 78 chromosomes in their somatic cells. The exceptions are the red wolf and

How many chromosomes do dogs have in their reproductive cells? Germ cells always have two times fewer chromosomes than somatic cells. Because they are distributed equally between daughter cells during meiosis.

In addition to dogs and wolves, the canine family also includes foxes. There are 78 chromosomes in a dog's karyotype. How many chromosomes do foxes have? Taxonomic genera of foxes are very heterogeneous in the number of chromosomes. The common fox has 38. The sand fox has 40. The Bengal fox has 60.

How many chromosomes are there in a dog's red blood cells?

Red blood cells are red blood cells that serve as oxygen carriers. How are they structured? Mature red blood cells must contain a large amount of hemoglobin. That is why they do not have many organelles, including chromosomes, since there is no nucleus at all.

However, in the blood of dogs, as in the blood of humans, there are reticulocytes - immature red blood cells. They make up only 1-2 percent of the total number of red blood cells. Reticulocytes contain ribosomal RNA, mitochondria, ribosomes, and the Golgi complex. But after a day or a day and a half, reticulocytes are transformed into mature red blood cells, which do not contain DNA, and, consequently, chromosomal structures.

How many chromosomes are in the karyotype of other animals

Animal species are very diverse in karyotype. Moreover, the number of chromosomes in the nuclei of cells of various animals does not depend on the complexity of the organization of a living being. For example, in a somatic cell of a frog there are 26 chromosomes. Chimpanzees have 48, which is slightly more than humans. Domestic chicken has 78 structures. This is the same number of chromosomes in dogs. The carp has 104, and the lamprey, a jawless vertebrate, has 174.

Chromosome set of plants

The karyotype of plant forms is also extremely diverse. Bread wheat with a hexaploid set of chromosomes has 42 information structures, rye has 14, and corn has 20. Tomatoes have 24 chromosomes in each cell, and rice has the same number. Jerusalem artichoke has 102.

There are absolute record holders in the number of chromosomes in the plant kingdom. These are ferns.

There are about 1200 chromosomes in the cell of this ancient plant. Horsetail has many such structures: 216.

Thus, all eukaryotic cells, except erythrocytes, have chromosomes. Depending on the type of animal or plant, the quantitative composition of chromosomes changes, as well as their size and shape. It is precisely because chromosomes have different sizes that the number of these structures is so different. The smaller the structures, the more likely their number will be greater.

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 sex 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.).

Containing genes. The name "chromosome" comes from the Greek words (chrōma - color, color and sōma - body), and is due to the fact that when cells divide, they become intensely colored in the presence of basic dyes (for example, aniline).

Many scientists, since the beginning of the 20th century, have thought about the question: “How many chromosomes does a person have?” So, until 1955, all the “minds of humanity” were convinced that the number of chromosomes in humans is 48, i.e. 24 pairs. The reason was that Theophilus Painter (Texas scientist) incorrectly counted them in preparative sections of human testes, according to a court decision (1921). Subsequently, other scientists, using different calculation methods, also came to this opinion. Even after developing a method for separating chromosomes, the researchers did not challenge Painter’s result. The error was discovered by scientists Albert Levan and Jo-Hin Thio in 1955, who accurately calculated how many pairs of chromosomes a person has, namely 23 (more modern technology was used to count them).

Somatic and germ cells contain a different chromosome set in biological species, which cannot be said about the morphological characteristics of chromosomes, which are constant. have a doubled (diploid set), which is divided into pairs of identical (homologous) chromosomes, which are similar in morphology (structure) and size. One part is always of paternal origin, the other of maternal origin. Human sex cells (gametes) are represented by a haploid (single) set of chromosomes. When an egg is fertilized, haploid sets of female and male gametes are united in one zygote nucleus. In this case, the double dialing is restored. It is possible to say with accuracy how many chromosomes a person has - there are 46 of them, with 22 pairs of them being autosomes and one pair being sex chromosomes (gonosomes). Sexes have differences - both morphological and structural (gene composition). In a female organism, a pair of gonosomes contains two X chromosomes (XX-pair), and in a male organism, one X- and a Y-chromosome (XY-pair).

Morphologically, chromosomes change during cell division, when they double (with the exception of germ cells, in which duplication does not occur). This is repeated many times, but no change in the chromosome set is observed. Chromosomes are most noticeable at one of the stages of cell division (metaphase). During this phase, the chromosomes are represented by two longitudinally split formations (sister chromatids), which narrow and unite in the area of ​​the so-called primary constriction, or centromere (an obligatory element of the chromosome). Telomeres are the ends of a chromosome. Structurally, human chromosomes are represented by DNA (deoxyribonucleic acid), which encodes the genes that make up them. Genes, in turn, carry information about a specific trait.

Individual development will depend on how many chromosomes a person has. There are such concepts as: aneuploidy (change in the number of individual chromosomes) and polyploidy (the number of haploid sets is greater than the diploid one). The latter can be of several types: loss of a homologous chromosome (monosomy), or appearance (trisomy - one extra, tetrasomy - two extra, etc.). All this is a consequence of genomic and chromosomal mutations, which can lead to pathological conditions such as Klinefelter syndrome, Shereshevsky-Turner syndrome and other diseases.

Thus, only the twentieth century gave answers to all questions, and now every educated inhabitant of planet Earth knows how many chromosomes a person has. The sex of the unborn child depends on the composition of the 23 pairs of chromosomes (XX or XY), and this is determined during fertilization and the fusion of the female and male reproductive cells.

Genetic research of the human body is one of the most necessary for the population of the entire planet. It is genetics that is of great importance for studying the causes of hereditary diseases or predisposition to them. We'll tell you how many chromosomes does a person have, and what this information may be useful for.

How many pairs of chromosomes does a person have?

The cell of the body is designed to store, implement and transmit hereditary information. It is created from a DNA molecule and is called a chromosome. Many people are interested in the question of how many pairs of chromosomes a person has.

Humans have 23 pairs of chromosomes. Until 1955, scientists erroneously calculated the number of chromosomes to be 48, i.e. 24 pairs. The error was discovered by scientists using more precise techniques.

The set of chromosomes is different in somatic and germ cells. The doubled (diploid) set is present only in the cells that determine the structure (somatics) of the human body. One part is of maternal origin, the other part is of paternal origin.

Gonosomes (sex chromosomes) have only one pair. They differ in gene composition. Therefore, depending on gender, a person has a different composition of the pair of gonosomes. From the fact how many chromosomes do women have, The gender of the unborn child does not depend. A woman has a set of XX chromosomes. Its reproductive cells do not influence the development of sexual characteristics during fertilization of the egg. Belonging to a particular gender depends on the information code about how many chromosomes does a man have. It is the difference between the XX and XY chromosomes that determines the sex of the unborn child. The remaining 22 pairs of chromosomes are called autosomal, i.e. the same for both sexes.

• A woman has 22 pairs of autosomal chromosomes and one pair XX;
• A man has 22 pairs of autosomal chromosomes and one XY pair.

The structure of chromosomes changes during division in the process of doubling somatic cells. These cells are constantly dividing, but the set of 23 pairs has a constant value. The structure of chromosomes is influenced by DNA. The genes that make up the chromosomes form a specific code under the influence of DNA. Thus, the information obtained during the DNA coding process determines the individual characteristics of a person.

Changes in the quantitative structure of chromosomes

A person's karyotype determines the totality of chromosomes. Sometimes it can be modified due to chemical or physical reasons. The normal number of 23 chromosomes in somatic cells can vary. This process is called aneuploidy.

1. The number may be less, then this is monosomy.
2. If there is no pair of autotenous cells, then this structure is called nullisomy.
3. If a third chromosome is added to a pair of cells that make up a chromosome, then this is trisomy.

Various changes in the quantitative set lead to a person receiving congenital diseases. Abnormalities in the structure of chromosomes cause Down syndrome, Edwards syndrome and other conditions.

There is also a variation called polyploidy. With this deviation, a multiple increase in chromosomes occurs, that is, a doubling of a pair of cells that is part of one chromosome. A diploid or germ cell can be present three times (triploidy). If it is present 4 or 5 times, then this increase is called tetraploidy and pentaploidy, respectively. If a person has such a deviation, then he dies within the first days of life. The plant world is quite widely represented by polyploidy. A multiple increase in chromosomes is present in animals: invertebrates, fish. Birds with this anomaly die.

MOSCOW, July 4— RIA Novosti, Anna Urmantseva. Who has the larger genome? As you know, some creatures have a more complex structure than others, and since everything is written in DNA, then this should also be reflected in its code. It turns out that a person with his developed speech must be more complex than a small round worm. However, if you compare us with a worm in terms of the number of genes, you get about the same thing: 20 thousand genes of Caenorhabditis elegans versus 20-25 thousand of Homo sapiens.

Even more offensive for the “crown of earthly creatures” and the “king of nature” are comparisons with rice and corn - 50 thousand genes in relation to human 25.

However, maybe we think wrong? Genes are “boxes” in which nucleotides are packaged—the “letters” of the genome. Maybe count them? Humans have 3.2 billion nucleotide pairs. But the Japanese crow's eye (Paris japonica) - a beautiful plant with white flowers - has 150 billion base pairs in its genome. It turns out that a person should be 50 times simpler than some flower.

And the lungfish protoptera (lungfish - having both gill and pulmonary respiration) turns out to be 40 times more complex than humans. Maybe all fish are somehow more complex than people? No. The poisonous fugu fish, from which the Japanese prepare a delicacy, has a genome eight times smaller than that of humans and 330 times smaller than that of the lungfish Protoptera.
All that remains is to count the chromosomes - but this confuses the picture even more. How can a person be equal in number of chromosomes to an ash tree, and a chimpanzee to a cockroach?

Evolutionary biologists and geneticists encountered these paradoxes a long time ago. They were forced to admit that the size of the genome, no matter how we try to calculate it, is strikingly unrelated to the complexity of the organization of organisms. This paradox was called the “C-value mystery,” where C is the amount of DNA in the cell (C-value paradox, the exact translation is “genome size paradox”). And yet some correlations between species and kingdoms exist.

© Illustration by RIA Novosti. A. Polyanina

© Illustration by RIA Novosti. A. Polyanina

It is clear, for example, that eukaryotes (living organisms whose cells contain a nucleus) have, on average, larger genomes than prokaryotes (living organisms whose cells do not contain a nucleus). Vertebrates have, on average, larger genomes than invertebrates. However, there are exceptions that no one has yet been able to explain.

There have been suggestions that genome size is related to the length of an organism's life cycle. Using plants as an example, some scientists have argued that perennial species have larger genomes than annuals, usually with a difference of several times. And the smallest genomes belong to ephemeral plants, which go through the full cycle from birth to death within a few weeks. This issue is currently being actively discussed in scientific circles.

Explains the leading researcher at the Institute of General Genetics. N.I. Vavilova of the Russian Academy of Sciences, Professor of the Texas Agromechanical University and the University of Gottingen Konstantin Krutovsky: “The size of the genome is not related to the duration of the life cycle of the organism! For example, there are species within the same genus that have the same genome size, but may differ in life expectancy tens, if not hundreds of times. In general, there is a connection between genome size and evolutionary advancement and complexity of organization, but with many exceptions. Generally, genome size is associated with ploidy (copy number) of the genome (and polyploids are found in both plants and animals) and amount of highly repetitive DNA (simple and complex repeats, transposons and other mobile elements)."

There are also scientists who have a different point of view on this issue.