Do vegetables have chromosomes? DNA record holders: how the genomes of humans and worms relate to each other

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 found that the number of chromosomes in different types 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.

U female body a pair of gonosomes contains two X chromosomes (XX-pair), and in a male, one X- and 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.).

From school biology textbooks, 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, the smallest number is earthworms and ants. 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.

On a 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 are of economic importance, the number of these molecules is as follows:

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

Informative! 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, each animal has a different number of 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:

Video

​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 a chromosome is?

− 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 at the end of the 19th 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 characteristics 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 humans 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?

Are there any interesting examples of 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, the 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?

− 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.

Did Charles Darwin renounce his theory of human evolution at the end of his life? Did ancient people find dinosaurs? Is it true that Russia is the cradle of humanity, and who is the yeti - perhaps one of our ancestors, lost through the centuries? Although paleoanthropology - the science of human evolution - is booming, the origins of man are still surrounded by many myths. These are anti-evolutionist theories and legends generated by popular culture, and pseudo-scientific ideas that exist among educated and well-read people. Do you want to know how everything “really” was? Alexander Sokolov, editor-in-chief of the portal ANTHROPOGENES.RU, collected a whole collection of similar myths and checked how valid they are.

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

Let us remind our dear readers that chromosomes are the things in which DNA is packaged in our cells. Humans have 23 pairs of chromosomes (23 we got from our mom and 23 from our dad. Total is 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 is important, but the genes that these chromosomes contain. The same set of genes can be packaged 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 they contain remains the same. (Imagine that a wall was broken between two adjacent rooms. The result is one large room, but the contents - furniture and parquet flooring - are the same...)

The fusion of chromosomes occurred in our ancestor. This 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 similarity of human and chimpanzee genes?

In the 1970s, when biologists learned to compare the genetic sequences of different species, they did this for humans and chimpanzees. The 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 amounted to 1.1%,– wrote the famous Soviet primatologist E.P. Friedman in the book “Primates”. -... Species of frogs or squirrels within the same genus differ from each other 20–30 times more than chimpanzees and humans. This was so surprising that it was urgently necessary to somehow explain the discrepancy between the molecular data and what is known at the level of the whole organism» .

And in 1980, in a reputable magazine Science An article by a team of geneticists at the University of Minneapolis was published: The Striking Resemblance of High-Resolution G-Banded Chromosomes of Man and Chimpanzee (“Striking similarity of high-resolution stained chromosomes of humans and chimpanzees”).

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

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

But how does such a merger happen? Let's say that one of our ancestors had two chromosomes combined into one. He ended up with an odd number of chromosomes - 47, while the rest of the non-mutated individuals still had 48! And how did such a mutant then reproduce? How can individuals with different numbers of chromosomes interbreed?

It would seem that the number of chromosomes clearly distinguishes species from each other and is an insurmountable obstacle to hybridization. Imagine the surprise of the researchers when, while studying the karyotypes of various mammals, they began to discover variations in the number of chromosomes within some species! Thus, in different populations of the common shrew this figure can range 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 humans from chimpanzees: animals living in the south of Hindustan and Sri Lanka , have 15 pairs of chromosomes in their karyotype, and all other shrews from Arabia to the islands of Oceania have 20 pairs... It turned out that the number of chromosomes decreased because five pairs of chromosomes of a typical variety merged with each other: 8th with 16th, 9? I’m from 13th, etc.”

Mystery! Let me remind you that during meiosis - cell division, which results in the formation of sex cells - each chromosome in the cell must connect with its homologue pair. And then, when fused, an unpaired chromosome appears! Where should she go?

It turns out that the problem is solved! P. M. Borodin describes this process, which he personally recorded in 29-chromosomal punares. Punare are bristly rats native to Brazil. Individuals with 29 chromosomes were obtained by crossing between 30- and 28-chromosomal punares 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 the 28-chromosomal parent, and on the other, two shorter ones, which came from the 30-chromosomal parent. At the same time, each chromosome fell into place.”

Recent genetic studies of dolphins suggest that the ancestors of animals are ungulates. These are their closest relatives. The answer to the question about how many chromosomes do dolphins have, suggests a hypothesis about the primary habitation of these mammals on land.

How many chromosomes do dolphins have?

Chromosomes are a special structure that makes up DNA. It is located in the nucleus of the body's cell. The task of the chromosome is to store information about the structure of the body, its individual characteristics and gender. The dolphin has 44 chromosomes. Since they are located in double numbers in the cells, there are 22 pairs in total. A certain set of chromosomes establishes the karyotype of any representative of the animal or plant world.

Number of chromosomes in other sea inhabitants:

1. Penguin - 46.
2. Blue whale – 44.
3. Sea urchin – 42.
4. Shark – 36.
5. Seal – 34.

Dolphins belong to the species of cetaceans, the subspecies being toothed whales (dolphins, sperm whales, killer whales). There are about 50 species of dolphins in total. They primarily live in seawater, but there are a few species that live in large rivers. Dolphins, like land animals, are warm-blooded, viviparous, and feed their young with their milk. They breathe through their lungs; to do this, they emerge from the water several times during the day. A dolphin is completely different from a shark. The sea predator belongs to the class of fish, since it has gills, and its offspring do not feed on milk. The shark simply does not have milk.

Genetic research

Dolphins communicate with us

The existing theory about the origin of man from apes has become less convincing after recent studies of dolphin chromosomes. As it turns out, humans and dolphins have striking similarities in their chromosomal structures. Among other organisms living on earth, the dolphin turned out to be closest to artiodactyls and hippopotamus. Many similarities were found with elephants. Humans, dolphins and elephants are distinguished by the proportional volume of their brain relative to their body. Special structure nervous system determines a significant number of synapses (nerve connections) and brain convolutions. These properties allow dolphins to learn quickly.

Dolphins have higher intelligence than monkeys. Marine life They recognize themselves in the mirror, understand the intonation of human speech, know how to imitate and strictly follow the rules that have developed in the pack. Cetaceans communicate using low-frequency sounds. Sea water contains magnesium sulfate, which absorbs high-frequency noise. Therefore, the inhabitants of the sea have learned to use sounds that can travel long distances in water.

The human genes responsible for sleep are simply modified in dolphins. Therefore, these mammals sleep in a special way. During the research, scientists discovered DNA that is responsible for keeping one half of the brain awake while the other is asleep. This happened during the process of mutation. Scientists have concluded that after humans, dolphins have the highest intelligence on the planet.