All cells in the human body contain DNA. Is DNA different in every cell type? What DNA is passed on to offspring? Deoxyribonucleic acid

Incredible Facts

DNA is the blueprint for our body, and without it, we wouldn't exist. It is a molecule that contains the genetic instructions for development and continues to function in every living organism.

DNA is in every cell of our body, telling it which proteins to produce. We inherit the DNA in our cells from our parents, so we have many similarities.

She has the shape double helix, similar to a huge spiral ladder, and each rung on this ladder consists of a pair of nucleotides. When DNA is copied, errors sometimes occur and these errors are known as mutations.

Here are some interesting facts about DNA that will help you understand yourself better.

DNA molecule

1. Bdelloid rotifers - These are microscopic animals that for 80 million years remained exclusively females. They reproduce by borrowing the DNA of other animals.

2. If you had to type one word per second for 8 hours a day, you would it took 50 years to print the human genome.

4. If you suddenly undergo a bone marrow transplant, in the DNA of your blood donor DNA will be present which has led to false arrests in the past.

5. With siblings 50% shared genes like parents with children.

6. DNA is damaged about 1 million times a day in every cell of our body. Fortunately, our body has a complex system for its recovery. If this were not the case, it would lead to cancer or cell death.

7. When it comes to invertebrates, then earthworms are our closest relatives. We have more DNA in common than cockroaches and even octopuses.

8. Four families in Iceland have DNA found only in Native Americans, according to scientists. Evidence indicates that the Vikings brought a Native American woman back to Europe about 1,000 years ago.

9. The International Space Station has a hard drive called " disc of immortality". It contains the DNA of people like Lance Armstrong and Stephen Hawking in case of a worldwide catastrophe.

10. Brooke Greenberg, the girl who looked like a child all her life, died at the age of 20. Scientists believe that it DNA could be the key to biological immortality.

Human DNA

11. Around 8 percent of our DNA is made up of ancient viruses that once infected humans.

12. According to DNA research, the Polynesians visited Chile in the 1300s and overtook Columbus by setting foot in the Americas almost 200 years earlier.

13. Around 2 grams of DNA could hold all of the world's digitally stored information.

14. Scientists recorded a song from the Disney cartoon("It"s A small world After All") in bacterial DNA, which is resistant to radioactivity, so that in case nuclear disaster humans in the future or other life forms were able to find it.

15. Zambian doctor John Schneeberger was accused of sexual assault. He implanted himself with a tube with the blood of another person, and when they took blood from him for DNA, he was able to deceive the experts. In the end, he still managed to detain.

16. Human DNA is 99.9 percent the same. The differences are the last 0.1 percent.

17. The genetic content of an egg can be replaced with a male's DNA and then fertilized with a sperm. Thus, two men can become the parents of a child.

18. The DNA in all your cells can stretch over 16 billion kilometers if it is unrolled. This is approximately the distance from Earth to Pluto and back.

19. Although there are websites that offer genetic tests on saliva that confirm your lineage, scientists warn that this is a kind of "genetic astrology" and should not be taken seriously.

20. 50 percent of your DNA is similar to that of a banana.

21. Scientists have determined that the half-life of DNA is 521 years, and after 1.5 million years, even DNA preserved in its best form will not be readable.

22. Due to the destruction of DNA, it is unlikely that we will ever be able to clone dinosaurs or other prehistoric animals.

23. German police once took DNA samples during a jewelry robbery. The samples pointed to the twins Hassan and Abbas O. Both denied involvement in the crime, despite the fact that the police knew that one of them had committed the crime.

They could not determine which of them did it, since the DNA was almost identical, and according to German law, suspects could not be kept. indefinite term. Thus, the police had no other choice but to release the suspects.

24. All people of non-African descent have traces of Neanderthal DNA.

25. During the Hornslet Deep Burial Project, a Danish artist Christian von Hornslet in 2013 to the deepest part of the oceanthe time capsule was lowered. The capsule contained blood, hair and animal DNA samples. The aim of the project was preservation of DNA so that extinct species can be brought back to life in the future.

What does DNA mean

What does DNA mean

(or a set of measuring instruments) that ensures the reproduction and (or) storage of a unit, as well as the transfer of its size to lower measuring instruments according to the verification scheme and approved as a standard in the prescribed manner. Wiki

Approved by whom? And why can't the established order change? There are several cells in our body that are not subject to the standard known to science, according to which all cells are mortal, finite. These rebels violate the accepted patterns and are called reference, contrary to the accepted order. These cells live in us from birth until death and contain the original, uncontaminated DNA matrix of our body, and DNA, as we remember, is bioacoustic, capable of reading from info-fields all new options for auto-modification in one direction or another (destruction / improvement). Reference cells can be activated to the extent possible of the organism - their field structures can be transferred to neighbors in order to resume work without distortion caused by the environment in which the organism lives and is exposed. The carriers of the reference program are able to regenerate practically without time limits, they do not have the "aging" function, or it is slowed down by several orders of magnitude. In other words, if we achieve the activation of reference cells throughout our body, we will come closer to immortality by a dozen steps. Let's talk about them.

A: Can you imagine how much energy is contained in one gram of meat or stone? And all this dense energy contains a huge amount of energy and very little information. It (from thin layers) is very difficult to reach and difficult to change. And you need to get to the first eight cells. When conception occurs, division occurs: the first two cells, four, eight ... The first eight cells are practically immortal, they live from the beginning of the birth of the body to death, until wooden box. All other cells live no more than seven years. Only the first eight cells that emerged from a fertilized egg live from beginning to end. These eight cells are located in the very middle of the chest, this is the material projection of the spiritual heart.

The scientists of this world know that these first eight cells are immortal, they live as long as the physical body lives. In these cells, among other things, there are standards of genetic matrices. Those. mutations may affect the periphery, but by no means this center. So the center, the heart is everything: if it is damaged, then an irreversible genetic mutation occurs, the being turns into a being of chaos. It is called "chaos in his heart", "not of this world heart." When the middle suffers - where the matrix of primary light is contained (and the matrix of primary light is, in fact, the laws of the golden section, and so on, which allows you to feel harmony, namely to feel and see directions towards evolution, towards increasing harmony, decreasing entropy) if this is destroyed, then the movement to happiness turns into a "Brownian movement", so that the being cannot determine what is beautiful and what is ugly.

Q: These eight cells are exactly in the heart?
A: They are in the very middle of your chest, in the very middle of you. Only people think that the child grows from top to bottom. It is only grass that grows from the earth to the sun, while a person grows from the middle in all directions - your legs grow down, your head grows upwards, arms to the sides, the very center from which you grow is located in the very middle of your chest *.

*all details of this conversation are personal to the operator. Other sessions have shown that the reference cells in each of us can be in different places. There can be 4, 8, 12 or more. They can be together or separately, but everyone has them. The crystal in the chest is directly related to the reference cells - it feeds them with energy information and has a protective function. And yes, some call it "plasma DNA"

Q: Can these cells be physically distinguished from the rest somehow?
A: Yes, they are larger than others and they do not age. They die only because the body dies. The rest of the cells age, die, are replaced by others, but these cells lack the mechanism of aging. They are virtually immortal.

Q: Did the program of immortality extend to the rest of the cells before?
A: Let's just say that death was not a biomechanical program, but a conscious choice. It didn't happen like that before. In normal space, not in this distorted one, the body could live several circles of life. In principle, if you feed and practice the practices, you could support the body for as long as you like, almost forever. If you wanted to leave the incarnation, you went to bed with a clear certainty that "I fall asleep and leave this world." Then in a dream (and you fell asleep deeper than usual) disidentification took place, the consciousness flew away from the body, and the body simply fell asleep and did not wake up *. Those. death was like a father telling his children: "I'm tired of living, I'm giving you everything, I'm leaving" - he fell asleep and died. No one has ever died of disease, it was not foreseen.
*sometimes such care was practiced in meditation, sometimes with the help of priests

Q: And where did illnesses and so on come from in this case? Who originally introduced the program?
A: When our Creator let the virus in. He was the first to fall ill. From him, from His female incarnations, the distortion began - two "male" Creators, and one "female". Because of this, all energy flows are disrupted, the connection with the Higher Self is disrupted, and Free Will with separation from God is obtained. After all, what is Free Will? Imagine your body, it acts as a single harmonious whole, each cell also has its own consciousness, but all actions are aimed at maintaining the homeostasis of the whole organism. And if every cell starts to act as it wants, then this is called cancer in the body. In a global sense, after the virus came here, cancer also began in our creation, because every creature separated from God and began to act according to the principle “what I want, I turn back”, and the Higher Self is not a decree for me.

VYa means the heavenly VYa, Brahman, Aham Brahma Asmi - this is it. There is no single coordination, therefore, from the moment the virus “ate” one of the female incarnations of our Creator, the first thing that started here was games of war. It started something like the following, the numbers are purely arbitrary, you can imagine the events something like this: seventy children of God were created, they are powerful creatures, they were neither light nor dark, they shared it like in the yard - 35 play for the "Red Army", 35 - for "fascists", and began to fall down the vibrations.

The lower they fell, the more they forgot that the war is a "fun yard war" and began to believe in their mission. At the lower levels, the Dark Ones began to fight with the Light Ones quite seriously. Such is the entertainment.

From another session:

Q: Technique* for working with reference cells, pulling rays out of oneself. What is it and why is it given?
A: This is shell recovery.
Q: How often should this be done?
O: How do you feel.
Q: Does it make sense to do this daily?
A: If you feel that way. Pay attention to the shell. Deadlines may change, rhythms may change. Follow your feelings.

*What technology are we talking about? About a very simple one:

Believe in the fact that you really have an endless source of life energy. For simplicity, call it "reference cells", although these cells are only a small part of this source. In each of us, they are contained in different places, it is not so difficult to find them, but the exact location is not so important. Even if you can't see them, just KNOW that they are within you.

If something starts to hurt (head, stomach, it doesn't matter), with physical hands we make a movement of "pulling" the field of reference cells out of ourselves.
With three fingers we grab a "pinch" of the field, pull it away from us and release (unclench our fingers) it at arm's length through the aching organ, as if you are pulling pure light from yourself (through the organ), which restores the work of diseased cells, burns out pain, regenerates.

From the outside, it will look like you are quickly removing a lot of fluff from yourself (you need to make a couple of dozen movements before the pain starts to pass).

For advanced users:

Ask to see the cells in meditation, they will show you. Further, with the help of the guardian or on our own, we put forward the reference field (glow) to the size of our own physical body, we can go beyond it, direct it to the diseased organ, fix the sensations, remember them if necessary. Over time, it is no longer necessary to move the physical hand, it is enough to move the etheric hand ("imagine"). The practice not only has a powerful healing potential, but also helps in expanding the boundaries thin bodies, thickening the aura and filling gaps.

Check if it works)

THEMATIC SECTIONS:
| | | |

What is better for nature: to buy a live Christmas tree or an artificial one? This is very complex issue, to which we will try to answer as simply as possible, based on the "carbon footprint" left by living and artificial tree, - that is, the amount of greenhouse gases emitted during the life cycle of a product. The Carbon Trust estimates that a two-meter-sized live Christmas tree leaves the equivalent of 16 kg of carbon dioxide if discarded after use, and only 3.5 kg if burned. Rotting causes the production of methane, which creates a much stronger the greenhouse effect than carbon dioxide itself. According to the same data, a two-meter artificial Christmas tree leaves a "carbon footprint" of 40 kg of CO 2 . So if you choose this option, try to use this tree longer. Why do people hiccup? Not only humans hiccup: these convulsive spasms of the diaphragm from time to time torment all mammals and many other animals that use pulmonary respiration. Short and strong movements create sharp breaths that are interrupted by a sudden occlusion of the airways, creating the characteristic sound of hiccups. This involuntary reaction is supposed to help expel air from the stomach. But it can also be the result of accidental irritation of the vagus nerve, which passes through the same opening in the diaphragm as the esophagus. Therefore, hiccups can cause too hasty absorption of food. There is also a hypothesis that hiccups are a relic left to us from dizzyingly distant times. At any rate, amphibians breathe through very similar spasms that allow their gills to be washed over. Can you get a cold from your dog?
Unlikely: most cases of SARS occur due to rhinoviruses, which, as a rule, specialize in infecting a particular species. Animals have their cold strains, we have ours. On the other hand, the influenza virus is more flexible, and cases of transmission of "swine" or "bird" flu to humans are rare, but widely known. But bacteria - pathogens are much more universal, and streptococci or tubercle bacilli that cause angina can both infect your dog and become infected from it. Is it possible to harm a person by pointing a thousand laser pointers at him? The laser in the pointer can damage vision, but it is not felt by the skin. Usually these are systems with a power of less than 5 mW, according to GOST they must be marked with warning labels, but their sales are not limited. If you came up with the idea to destroy the enemy with laser pointers, then hundreds will not be enough. University of Texas physicist Rebecca Thompson has calculated that for a beam that enters the eye to be able to penetrate and damage the brain, it would take at least 1 kW of power - which means at least 200,000 pointers focused at one point. Theoretically, they can be placed on a large parabolic "dish", concentrating radiation on the victim. Which body cells do not have DNA?
Initially, DNA is present in all our cells, but during the adult stages of life, some of them lose the nucleus and the chromosomes contained in it. Thus, keratinized keratinocytes of the upper layers of the skin end their lives without a nucleus and major organelles. Platelets also do not have a nucleus - pieces of cytoplasm that have separated from megakaryocyte cells. The best-known example is the oxygen-carrying red blood cells, which, as a result, are drastically reduced in size and can move through thin capillaries. Mature erythrocytes do not even have mitochondria that could contain extranuclear DNA.

How do astronauts live on the ISS? Sunrises and sunsets on the ISS occur every hour and a half. The sun can no longer set a comfortable rhythm of sleep and wakefulness. But astronauts observe the same habitual cyclicity. 24 hours are broken down into 6.5 hours of working time, 2.5 hours of training on simulators, an hour for lunch, the rest is rest and sleep. Usually the rise is announced at 6:00, work begins at 8:00 and ends at 19:00, lights out at 21:30. Time is counted according to Greenwich Mean Time, that is, four hours behind Moscow. Why is Pluto not a planet?
Almost half a century after the first observation of Pluto, its dimensions remained exactly unknown. Only in 1978, when the satellite Charon was discovered, was it possible to determine the mass, and then the diameter of Pluto, which was only 2370 km. For comparison, the diameter of the Moon is 3475 km. In the Kuiper belt, where Pluto is located, there are many bodies comparable in size, and Eris is even heavier. The discovery of Eris in 2005 was the last straw: it was necessary either to rank it as a planet, and dozens of bodies similar to Pluto, or to exclude Pluto itself from their number. The decision was made in 2006: a solar system planet is now considered a body orbiting the Sun, not a satellite of one of the planets, massive enough to take on a rounded shape and clear the vicinity of its orbit. Pluto, as well as Eris, Ceres and many others do not satisfy the third condition and do not reach full-fledged planets.

ATTENTION!!! THIS MATERIAL HAS BEEN REVISED, ADDED AND INCLUDED IN THE BOOK “Creation or Evolution? How old is the Earth? PLEASE GO TO THE PAGE TO READ -->

To be convinced of the absurdity of spontaneous generation, let's see how the microcosm works. Note that we will consider it only superficially, since it is too complicated.

A cell is an elementary unit of structure and vital activity of all living organisms. It has its own metabolism, is capable of independent existence, self-reproduction and development. Each cell is a city in miniature, consisting of power plants, overpasses, treatment facilities, etc. A cell consists of a nucleus, membrane, cytoplasm, chromosomes, ribosomes, DNA, RNA, proteins and many other elements, each of which, in turn, has its own microcosm. Naturally, a cell can exist and perform its functions if all these structures are created simultaneously.

A protein molecule (protein) consists of 50 - 40,000 amino acids interconnected.

Rice. The principle of the structure of a protein from amino acids

Moreover, the diversity of protein structures created from 20 types of amino acids cannot be overestimated. So, a chain of 100 amino acids (a small protein) can be represented in more than 10 to the 130th power, in other words, 10 and 130 zeros. For example: in the oceans there are 10 to the 40th degree of water molecules (10 and 40 zeros). Moreover, the location of each amino acid in the protein structure is of great importance, as in computer program. If at least one element is rearranged, the protein molecule will not work, which means it will not be able to function and fulfill its purpose, and the cell, that is, the part of the body in which cells with these proteins are needed, will not work. Imagine how negligible the possibility of the spontaneous appearance of the simplest protein, and even more so the specific one that is needed by the cell and, as a result, the body, is negligible! But for the functioning of the simplest cells and organisms, thousands of different proteins are needed.

Without ribosomes and RNA, amino acids cannot combine into a protein, especially in the one that is needed at this stage in a particular cell. The RNA takes the information about this desired protein from the DNA, and the ribosomes act as a building block.

Rice. Protein synthesis in a cell

In a DNA molecule of human chromosomes, there are from 50 to 245 million complexly arranged pairs of nitrogenous bases. Biochemists have calculated that in 1 DNA molecule, there are 10 to 87 variants of the connection of the material in it. And only one option will allow you to create you personally - with all properly functioning organs and individual qualities. Materialistic scientists believe that the earth is 4.5 billion years old. This period of time corresponds to 10 to the 25th power of seconds. That is, if one variant of DNA is invented every second, then the age of the Earth will not be enough to create one functioning DNA. But it's not just the sheer complexity of DNA. The fact is that DNA is a program that can be compared to a computer code. Only this code surpasses the programs created by man in its size and complexity. The famous programmer Bill Gates said this about DNA: "Human DNA is like a computer program, only infinitely more perfect." Think about it, since there is a program, then a reading mechanism is also needed, otherwise any program is just garbage. So, DNA also contains a code for creating a mechanism for reading information from itself and further building the whole organism according to this program. It is written in DNA where and at what time a certain protein and other elements should be created in a person. From one cell in which DNA is located, the self-construction of any organism begins. The structure of the DNA molecule allows it to divide. It consists of two parallel identical strands of nucleotides linked by a weak chemical hydrogen bond. When the molecule divides, the chain breaks, leaving all the information in each of the resulting new cells.

Rice. DNA structure

Who created the material for the cell? Who connected this material into a cage? Who came up with different - different from each other, intended for different functions, but necessary for each organism cells. Who wrote the information in the form of a program in DNA? Who created the mechanism for reading and executing this information? A scientific documentary filmed about the ingenious complexity of the cell " Miracle in a cage (miracle in a cage)", in which it is shown in the form of animation what extremely complex processes take place inside the cell. There are many videos about this "Cell Life", "Cell World", etc. To analyze Darwin's theory, you need to understand that in those days science could see only large bacteria, and the cell was presented to people as a tiny container with a liquid.Moreover, they knew nothing about microbiology and genetics.

Today, many scientists are aware of the incredible complexity of the structure of the cell and the whole organism. Some of them are on the side of the creationists. But many believe in chance. Thus, we see not the confrontation of scientists against religion, but two religions - 1) faith in God and creation, and 2) faith in the accidental happy birth of life and its further self-development. But even simple reason is enough to understand the practical impossibility of the latter. Think about how millions of inanimate elements, with the help of chemical bonds, organized themselves into complex huge structures of DNA, RNA, ribosomes, proteins, etc., following a strictly defined sequence (including a program), and then, "thinking through" and "distributing" interactions with each other, surrounding themselves with a shell, created a living organism out of itself - a cell with a huge variety of possibilities and functions. How then the cells, dividing, did not spread into jelly, but created separate organs, tissues, bones, blood vessels, the brain, which, interacting with each other in a complex way, formed a viable and capable of self-reproducing organism. Where did the masculine and feminine come from? If we assume that we evolved from an amoeba, then the fission theory would be more correct. How, in the process of evolution within a species, its representatives gradually divided into masculine and feminine, while maintaining viability and acquiring the ability to uniquely reproduce their own kind, and even different ways(internal, external, double fertilization…)? How did new creatures, for example, mammals, come into being when the structure of the female and male organisms was still in the process of separation and development? After all, underdeveloped spermatozoa, eggs and the uterus are simply not able to create a living being. How different-sex creatures and their organs developed in parallel while being viable. Today we see that even a small deviation or disease in the sperm, eggs and uterus makes a person infertile. And speaking of evolutionary development, the gradual improvement of everything, both external and internal, including the organs of reproduction, is simply inevitable. How did underdeveloped creatures with underdeveloped reproductive organs reproduce, and how did intermediate forms reproduce? The materialists do not have answers to these questions, and cannot be.

Here it is appropriate to recall a rhetorical question to which materialists will never be able to find an answer: "What was before the chicken or the egg?". Despite the seeming comical question, he is very serious. The chicken could not have come into existence without the egg, the perfect device for the formation of the embryo, the growth of the embryo, and its development into a chicken. So the egg could not suddenly appear out of nowhere without a chicken. This mutually exclusive analogy is superimposed on other controversial points in the materialistic theory of evolution. As noted above, any organism has DNA, which contains all the information about it. Without this ready-made DNA with information embedded in it, this perfect organism would not exist. So DNA can only be taken from an already created creature.

Sir Fred Hoyle, professor of astronomy at Cambridge, devoted much of his time to the mathematical calculation of the possibility of the accidental origin of life and subsequently stated: “It is more likely that a tornado rushing through a junkyard can assemble a Boeing 747 from trash thrown into the air than from inanimate nature can arise alive."

Therefore, science still cannot give a repeating example of the spontaneous generation of life!

CELL, MOLECULE, DNA - THE HUMAN MICROWORLD, LIFE INSIDE THE ORGANISM

The radiocarbon method is wrong

Earth's magnetic field is weakening

"Pierced" layers

Soil erosion at the initial level

The moon is less than 10,000 years old

Population Growth Corresponds to the Biblical Age of the Earth

Moon close to Earth

Ice rings show not years

The coral reef has been growing for less than 5,000 years

Dinosaurs are reliable witnesses

All humans are descended from the same pair

Civilizations and writing less than 5,000 years old

The layers of the Earth do not have their own dating. Geological layers. Geological scale

Lack of scientific evidence. Kent Hovind

On the right is the largest human DNA helix built from people on the beach in Varna (Bulgaria), which was included in the Guinness Book of Records on April 23, 2016

Deoxyribonucleic acid. General information

DNA (deoxyribonucleic acid) is a kind of blueprint of life, a complex code that contains data on hereditary information. This complex macromolecule is capable of storing and transmitting hereditary genetic information from generation to generation. DNA determines such properties of any living organism as heredity and variability. The information encoded in it determines the entire development program of any living organism. Genetically embedded factors predetermine the entire course of life of both a person and any other organism. Artificial or natural influence of the external environment can only slightly affect the overall severity of individual genetic traits or affect the development of programmed processes.

Deoxyribonucleic acid(DNA) is a macromolecule (one of the three main ones, the other two are RNA and proteins), which provides storage, transmission from generation to generation and implementation of the genetic program for the development and functioning of living organisms. DNA contains information about the structure of various types of RNA and proteins.

In eukaryotic cells (animals, plants, and fungi), DNA is found in the cell nucleus as part of chromosomes, as well as in some cell organelles (mitochondria and plastids). In the cells of prokaryotic organisms (bacteria and archaea), a circular or linear DNA molecule, the so-called nucleoid, is attached from the inside to cell membrane. They and lower eukaryotes (for example, yeast) also have small autonomous, mostly circular DNA molecules called plasmids.

From a chemical point of view, DNA is a long polymeric molecule consisting of repeating blocks - nucleotides. Each nucleotide is made up of a nitrogenous base, a sugar (deoxyribose), and a phosphate group. The bonds between nucleotides in a chain are formed by deoxyribose ( WITH) and phosphate ( F) groups (phosphodiester bonds).

Rice. 2. Nuclertide consists of a nitrogenous base, sugar (deoxyribose) and a phosphate group

In the overwhelming majority of cases (except for some viruses containing single-stranded DNA), the DNA macromolecule consists of two chains oriented by nitrogenous bases to each other. This double-stranded molecule is twisted in a helix.

There are four types of nitrogenous bases found in DNA (adenine, guanine, thymine, and cytosine). The nitrogenous bases of one of the chains are connected to the nitrogenous bases of the other chain by hydrogen bonds according to the principle of complementarity: adenine combines only with thymine ( A-T), guanine - only with cytosine ( G-C). It is these pairs that make up the "rungs" of the helical "ladder" of DNA (see: Fig. 2, 3 and 4).

Rice. 2. Nitrogenous bases

The sequence of nucleotides allows you to "encode" information about various types RNA, the most important of which are information or template (mRNA), ribosomal (rRNA) and transport (tRNA). All these types of RNA are synthesized on the DNA template by copying the DNA sequence into the RNA sequence synthesized during transcription and take part in protein biosynthesis (translation process). In addition to coding sequences, cell DNA contains sequences that perform regulatory and structural functions.

Rice. 3. DNA replication

The location of the basic combinations of DNA chemical compounds and the quantitative ratios between these combinations provide encoding of hereditary information.

Education new DNA (replication)

1. The process of replication: the unwinding of the DNA double helix - the synthesis of complementary strands by DNA polymerase - the formation of two DNA molecules from one.
2. The double helix "unzips" into two branches when enzymes break the bond between the base pairs of chemical compounds.
3. Each branch is a new DNA element. New base pairs are connected in the same sequence as in the parent branch.

Upon completion of the duplication, two independent helices are formed, created from the chemical compounds of the parent DNA and having the same genetic code with it. In this way, DNA is able to rip through information from cell to cell.

More detailed information:

STRUCTURE OF NUCLEIC ACIDS

Rice. 4 . Nitrogenous bases: adenine, guanine, cytosine, thymine

Deoxyribonucleic acid(DNA) refers to nucleic acids. Nucleic acids is a class of irregular biopolymers whose monomers are nucleotides.

NUCLEOTIDES consist of nitrogenous base, connected to a five-carbon carbohydrate (pentose) - deoxyribose(in the case of DNA) or ribose(in the case of RNA), which combines with a phosphoric acid residue (H 2 PO 3 -).

Nitrogenous bases There are two types: pyrimidine bases - uracil (only in RNA), cytosine and thymine, purine bases - adenine and guanine.

Rice. Fig. 5. The structure of nucleotides (left), the location of the nucleotide in DNA (bottom) and the types of nitrogenous bases (right): pyrimidine and purine

The carbon atoms in a pentose molecule are numbered from 1 to 5. Phosphate combines with the third and fifth carbon atoms. This is how nucleic acids are linked together to form a chain of nucleic acids. Thus, we can isolate the 3' and 5' ends of the DNA strand:

Rice. 6. Isolation of the 3' and 5' ends of the DNA strand

Two strands of DNA form double helix. These chains in a spiral are oriented in opposite directions. In different strands of DNA, nitrogenous bases are connected to each other by means of hydrogen bonds. Adenine always combines with thymine, and cytosine always combines with guanine. It is called complementarity rule.

Complementarity rule:

A-T G-C

For example, if we are given a DNA strand that has the sequence

3'-ATGTCCTAGCTGCTCG - 5',

then the second chain will be complementary to it and directed in the opposite direction - from the 5'-end to the 3'-end:

5'- TACAGGATCGACGAGC- 3'.

Rice. 7. The direction of the chains of the DNA molecule and the connection of nitrogenous bases using hydrogen bonds

DNA REPLICATION

DNA replication is the process of doubling a DNA molecule by template synthesis. In most cases of natural DNA replicationprimerfor DNA synthesis is short snippet (created again). Such a ribonucleotide primer is created by the enzyme primase (DNA primase in prokaryotes, DNA polymerase in eukaryotes), and is subsequently replaced by deoxyribonucleotide polymerase, which normally performs repair functions (correcting chemical damage and breaks in the DNA molecule).

Replication occurs in a semi-conservative manner. This means that the double helix of DNA unwinds and a new chain is completed on each of its chains according to the principle of complementarity. The daughter DNA molecule thus contains one strand from the parent molecule and one newly synthesized. Replication occurs in the 3' to 5' direction of the parent strand.

Rice. 8. Replication (doubling) of the DNA molecule

DNA synthesis- this is not such a complicated process as it might seem at first glance. If you think about it, then first you need to figure out what synthesis is. It is the process of bringing something together. The formation of a new DNA molecule takes place in several stages:

1) DNA topoisomerase, located in front of the replication fork, cuts the DNA in order to facilitate its unwinding and unwinding.
2) DNA helicase, following topoisomerase, affects the process of "unwinding" the DNA helix.
3) DNA-binding proteins carry out the binding of DNA strands, and also carry out their stabilization, preventing them from sticking to each other.
4) DNA polymerase δ(delta) , coordinated with the speed of movement of the replication fork, performs the synthesisleadingchains subsidiary DNA in the direction 5" → 3" on the matrix maternal strands of DNA in the direction from its 3" end to the 5" end (speed up to 100 base pairs per second). These events on this maternal strands of DNA are limited.

Rice. 9. Schematic representation of the DNA replication process: (1) Lagging strand (lag strand), (2) Leading strand (leading strand), (3) DNA polymerase α (Polα), (4) DNA ligase, (5) RNA -primer, (6) Primase, (7) Okazaki fragment, (8) DNA polymerase δ (Polδ ), (9) Helicase, (10) Single-stranded DNA-binding proteins, (11) Topoisomerase.

The synthesis of the lagging daughter DNA strand is described below (see below). scheme replication fork and function of replication enzymes)

For more information on DNA replication, see

5) Immediately after the unwinding and stabilization of another strand of the parent molecule, it joinsDNA polymerase α(alpha)and in the direction 5 "→3" synthesizes a primer (RNA primer) - an RNA sequence on a DNA template with a length of 10 to 200 nucleotides. After that, the enzymeremoved from the DNA strand.

Instead of DNA polymeraseα attached to the 3" end of the primer DNA polymeraseε .

6) DNA polymeraseε (epsilon) as if continues to lengthen the primer, but as a substrate embedsdeoxyribonucleotides(in the amount of 150-200 nucleotides). As a result, a solid thread is formed from two parts -RNA(i.e. primer) and DNA. DNA polymerase εworks until it encounters the primer of the previousfragment Okazaki(synthesized a little earlier). This enzyme is then removed from the chain.

7) DNA polymerase β(beta) stands in place ofDNA polymerases ε,moves in the same direction (5" → 3") and removes primer ribonucleotides while inserting deoxyribonucleotides in their place. The enzyme works until the complete removal of the primer, i.e. until a deoxyribonucleotide (even more previously synthesizedDNA polymerase ε). The enzyme is not able to link the result of its work and the DNA in front, so it leaves the chain.

As a result, a fragment of the daughter DNA "lies" on the matrix of the mother thread. It is calledfragment of Okazaki.

8) DNA ligase ligates two adjacent fragments Okazaki , i.e. 5 "-end of the segment, synthesizedDNA polymerase ε,and 3" chain end built-inDNA polymeraseβ .

STRUCTURE OF RNA

Ribonucleic acid(RNA) is one of the three main macromolecules (the other two are DNA and proteins) that are found in the cells of all living organisms.

Just like DNA, RNA is made up of a long chain in which each link is called nucleotide. Each nucleotide is made up of a nitrogenous base, a ribose sugar, and a phosphate group. However, unlike DNA, RNA usually has one rather than two strands. Pentose in RNA is represented by ribose, not deoxyribose (ribose has an additional hydroxyl group on the second carbohydrate atom). Finally, DNA differs from RNA in the composition of nitrogenous bases: instead of thymine ( T) uracil is present in RNA ( U) , which is also complementary to adenine.

The sequence of nucleotides allows RNA to encode genetic information. All cellular organisms use RNA (mRNA) to program protein synthesis.

Cellular RNAs are formed in a process called transcription , that is, the synthesis of RNA on a DNA template, carried out by special enzymes - RNA polymerases.

Messenger RNAs (mRNAs) then take part in a process called broadcast, those. protein synthesis on the mRNA template with the participation of ribosomes. Other RNAs undergo chemical modifications after transcription, and after the formation of secondary and tertiary structures, they perform functions that depend on the type of RNA.

Rice. 10. The difference between DNA and RNA in terms of the nitrogenous base: instead of thymine (T), RNA contains uracil (U), which is also complementary to adenine.

TRANSCRIPTION

This is the process of RNA synthesis on a DNA template. DNA unwinds at one of the sites. One of the chains contains information that needs to be copied onto the RNA molecule - this chain is called coding. The second strand of DNA, which is complementary to the coding strand, is called the template strand. In the process of transcription on the template chain in the 3'-5' direction (along the DNA chain), an RNA chain complementary to it is synthesized. Thus, an RNA copy of the coding strand is created.

Rice. 11. Schematic representation of transcription

For example, if we are given the sequence of the coding strand

3'-ATGTCCTAGCTGCTCG - 5',

then, according to the rule of complementarity, the matrix chain will carry the sequence

5'- TACAGGATCGACGAGC- 3',

and the RNA synthesized from it is the sequence

BROADCAST

Consider the mechanism protein synthesis on the RNA matrix, as well as the genetic code and its properties. Also, for clarity, on the link below, we recommend that you look at short video about the processes of transcription and translation occurring in a living cell:

Rice. 12. Process of protein synthesis: DNA codes for RNA, RNA codes for protein

GENETIC CODE

Genetic code- a method of encoding the amino acid sequence of proteins using a sequence of nucleotides. Each amino acid is encoded by a sequence of three nucleotides - a codon or a triplet.

Genetic code common to most pro- and eukaryotes. The table lists all 64 codons and lists the corresponding amino acids. The base order is from the 5" to the 3" end of the mRNA.

Table 1. Standard genetic code

1st the foundation nie	2nd base								3rd the foundation nie
	U		C		A		G
U	U U U	(Phe/F)	U C U	(Ser/S)	U A U	(Tyr/Y)	U G U	(Cys/C)	U
	U U C		U C C		U A C		U G C		C
	U U A	(Leu/L)	U C A		U A A	Stop codon**	U G A	Stop codon**	A
	U U G		U C G		U A G	Stop codon**	U G G	(Trp/W)	G
C	C U U		C C U	(Pro/P)	C A U	(His/H)	C G U	(Arg/R)	U
	C U C		C C C		C A C		C G C		C
	C U A		C C A		C A A	(Gln/Q)	CGA		A
	C U G		C C G		C A G		C G G		G
A	A U U	(Ile/I)	A C U	(Thr/T)	A A U	(Asn/N)	A G U	(Ser/S)	U
	A U C		A C C		A A C		A G C		C
	A U A		A C A		A A A	(Lys/K)	A G A		A
	A U G	(Met/M)	A C G		A A G		A G G		G
G	G U U	(Val/V)	G C U	(Ala/A)	G A U	(Asp/D)	G G U	(Gly/G)	U
	G U C		G C C		G A C		G G C		C
	G U A		G C A		G A A	(Glu/E)	G G A		A
	G U G		G C G		G A G		G G G		G

Among the triplets, there are 4 special sequences that act as "punctuation marks":

• *Triplet AUG, also encoding methionine, is called start codon. This codon begins the synthesis of a protein molecule. Thus, during protein synthesis, the first amino acid in the sequence will always be methionine.

• **Triplets UAA, UAG and UGA called stop codons and do not code for any amino acids. At these sequences, protein synthesis stops.

Properties of the genetic code

1. Tripletity. Each amino acid is encoded by a sequence of three nucleotides - a triplet or codon.

2. Continuity. There are no additional nucleotides between the triplets, information is read continuously.

3. Non-overlapping. One nucleotide cannot be part of two triplets at the same time.

4. Uniqueness. One codon can code for only one amino acid.

5. Degeneracy. One amino acid can be encoded by several different codons.

6. Versatility. The genetic code is the same for all living organisms.

Example. We are given the sequence of the coding strand:

3’- CCGATTGCACGTCGATCGTATA- 5’.

The matrix chain will have the sequence:

5’- GGCTAACGTGCAGCTAGCATAT- 3’.

Now we “synthesize” informational RNA from this chain:

3’- CCGAUUGCACGUCGAUCGUAUA- 5’.

Protein synthesis goes in the direction 5' → 3', therefore, we need to flip the sequence in order to "read" the genetic code:

5’- AUAUGCUAGCUGCACGUUAGCC- 3’.

Now find the start codon AUG:

5’- AU AUG CUAGCUGCACGUUAGCC- 3’.

Divide the sequence into triplets:

sounds like this: information from DNA is transferred to RNA (transcription), from RNA to protein (translation). DNA can also be duplicated by replication, and the process of reverse transcription is also possible, when DNA is synthesized from an RNA template, but such a process is mainly characteristic of viruses.

Rice. 13. Central dogma of molecular biology

GENOM: GENES AND CHROMOSOMES

(general concepts)

Genome - the totality of all the genes of an organism; its complete chromosome set.

The term "genome" was proposed by G. Winkler in 1920 to describe the totality of genes contained in the haploid set of chromosomes of organisms of the same biological species. The original meaning of this term indicated that the concept of the genome, in contrast to the genotype, is a genetic characteristic of the species as a whole, and not of an individual. With the development of molecular genetics, the meaning of this term has changed. It is known that DNA, which is the carrier of genetic information in most organisms and, therefore, forms the basis of the genome, includes not only genes in the modern sense of the word. Most of the DNA of eukaryotic cells is represented by non-coding (“redundant”) nucleotide sequences that do not contain information about proteins and nucleic acids. Thus, the main part of the genome of any organism is the entire DNA of its haploid set of chromosomes.

Genes are segments of DNA molecules that code for polypeptides and RNA molecules.

Over the past century, our understanding of genes has changed significantly. Previously, a genome was a region of a chromosome that encodes or determines one trait or phenotypic(visible) property, such as eye color.

In 1940, George Beadle and Edward Tatham proposed a molecular definition of a gene. Scientists processed fungus spores Neurospora crassa X-rays and other agents that cause changes in the DNA sequence ( mutations), and found mutant strains of the fungus that lost some specific enzymes, which in some cases led to disruption of the entire metabolic pathway. Beadle and Tatham came to the conclusion that a gene is a section of genetic material that defines or codes for a single enzyme. This is how the hypothesis "one gene, one enzyme". This concept was later extended to the definition "one gene - one polypeptide", since many genes encode proteins that are not enzymes, and a polypeptide can be a subunit of a complex protein complex.

On fig. 14 shows a diagram of how DNA triplets determine a polypeptide, the amino acid sequence of a protein, mediated by mRNA. One of the DNA strands plays the role of a template for the synthesis of mRNA, the nucleotide triplets (codons) of which are complementary to the DNA triplets. In some bacteria and many eukaryotes, coding sequences are interrupted by non-coding regions (called introns).

Modern biochemical definition of a gene even more specifically. Genes are all sections of DNA that encode the primary sequence of end products, which include polypeptides or RNA that have a structural or catalytic function.

Along with genes, DNA also contains other sequences that perform exclusively regulatory function. Regulatory sequences may mark the beginning or end of genes, affect transcription, or indicate the site of initiation of replication or recombination. Some genes can be expressed in different ways, with the same piece of DNA serving as a template for the formation of different products.

We can roughly calculate minimum gene size coding for the intermediate protein. Each amino acid in a polypeptide chain is encoded by a sequence of three nucleotides; the sequences of these triplets (codons) correspond to the chain of amino acids in the polypeptide encoded by the given gene. A polypeptide chain of 350 amino acid residues (medium length chain) corresponds to a sequence of 1050 bp. ( bp). However, many eukaryotic genes and some prokaryotic genes are interrupted by DNA segments that do not carry information about the protein, and therefore turn out to be much longer than a simple calculation shows.

How many genes are on one chromosome?

Rice. 15. View of chromosomes in prokaryotic (left) and eukaryotic cells. Histones are a broad class of nuclear proteins that perform two main functions: they are involved in the packaging of DNA strands in the nucleus and in the epigenetic regulation of nuclear processes such as transcription, replication, and repair.

As you know, bacterial cells have a chromosome in the form of a DNA strand, packed into a compact structure - a nucleoid. prokaryotic chromosome Escherichia coli, whose genome is completely decoded, is a circular DNA molecule (in fact, this is not a regular circle, but rather a loop without beginning and end), consisting of 4,639,675 bp. This sequence contains approximately 4300 protein genes and another 157 genes for stable RNA molecules. V human genome approximately 3.1 billion base pairs corresponding to almost 29,000 genes located on 24 different chromosomes.

Prokaryotes (Bacteria).

Bacterium E. coli has one double-stranded circular DNA molecule. It consists of 4,639,675 b.p. and reaches a length of approximately 1.7 mm, which exceeds the length of the cell itself E. coli about 850 times. In addition to the large circular chromosome as part of the nucleoid, many bacteria contain one or more small circular DNA molecules that are freely located in the cytosol. These extrachromosomal elements are called plasmids(Fig. 16).

Most plasmids consist of only a few thousand base pairs, some contain more than 10,000 bp. They carry genetic information and replicate to form daughter plasmids, which enter the daughter cells during the division of the parent cell. Plasmids are found not only in bacteria, but also in yeast and other fungi. In many cases, plasmids offer no advantage to the host cells and their only job is to reproduce independently. However, some plasmids carry genes useful to the host. For example, genes contained in plasmids can confer resistance to antibacterial agents in bacterial cells. Plasmids carrying the β-lactamase gene confer resistance to β-lactam antibiotics such as penicillin and amoxicillin. Plasmids can pass from antibiotic-resistant cells to other cells of the same or different bacterial species, causing those cells to also become resistant. Intensive use of antibiotics is a powerful selective factor that promotes the spread of plasmids encoding antibiotic resistance (as well as transposons that encode similar genes) among pathogenic bacteria, and leads to the emergence of bacterial strains with resistance to several antibiotics. Doctors are beginning to understand the dangers of widespread use of antibiotics and prescribe them only when absolutely necessary. For similar reasons, the widespread use of antibiotics for the treatment of farm animals is limited.

See also: Ravin N.V., Shestakov S.V. Genome of prokaryotes // Vavilov Journal of Genetics and Breeding, 2013. V. 17. No. 4/2. pp. 972-984.

Eukaryotes.

Table 2. DNA, genes and chromosomes of some organisms

	shared DNA, b.s.	Number of chromosomes*	Approximate number of genes
Escherichia coli(bacterium)	4 639 675		4 435
Saccharomyces cerevisiae(yeast)	12 080 000	16**	5 860
Caenorhabditis elegans(nematode)	90 269 800	12***	23 000
Arabidopsis thaliana(plant)	119 186 200		33 000
Drosophila melanogaster(fruit fly)	120 367 260		20 000
Oryza sativa(rice)	480 000 000		57 000
Mus muscle(mouse)	2 634 266 500		27 000
Homo sapiens(Human)	3 070 128 600		29 000

Note. Information is constantly updated; For more up-to-date information, refer to individual genomic project websites.

* For all eukaryotes, except yeast, the diploid set of chromosomes is given. diploid kit chromosomes (from Greek diploos - double and eidos - view) - a double set of chromosomes (2n), each of which has a homologous one.
**Haploid set. Wild strains of yeast typically have eight (octaploid) or more sets of these chromosomes.
***For females with two X chromosomes. Males have an X chromosome, but no Y, i.e. only 11 chromosomes.

A yeast cell, one of the smallest eukaryotes, has 2.6 times more DNA than a cell E. coli(Table 2). fruit fly cells Drosophila, a classic object of genetic research, contains 35 times more DNA, and human cells contain about 700 times more DNA than cells E. coli. Many plants and amphibians contain even more DNA. The genetic material of eukaryotic cells is organized in the form of chromosomes. Diploid set of chromosomes (2 n) depends on the type of organism (Table 2).

For example, in a human somatic cell there are 46 chromosomes ( rice. 17). Each chromosome in a eukaryotic cell, as shown in Fig. 17, a, contains one very large double-stranded DNA molecule. Twenty-four human chromosomes (22 paired chromosomes and two sex chromosomes X and Y) differ in length by more than 25 times. Each eukaryotic chromosome contains a specific set of genes.

Rice. 17. eukaryotic chromosomes.a- a pair of connected and condensed sister chromatids from the human chromosome. In this form, eukaryotic chromosomes remain after replication and in metaphase during mitosis. b- a complete set of chromosomes from a leukocyte of one of the authors of the book. Each normal human somatic cell contains 46 chromosomes.

If you connect the DNA molecules of the human genome (22 chromosomes and chromosomes X and Y or X and X) to each other, you get a sequence about one meter long. Note: In all mammals and other heterogametic male organisms, females have two X chromosomes (XX) and males have one X chromosome and one Y chromosome (XY).

Most human cells, so the total DNA length of such cells is about 2m. An adult human has about 10 14 cells, so the total length of all DNA molecules is 2・10 11 km. For comparison, the circumference of the Earth is 4・10 4 km, and the distance from the Earth to the Sun is 1.5・10 8 km. That's how amazingly compactly packaged DNA is in our cells!

In eukaryotic cells, there are other organelles containing DNA - these are mitochondria and chloroplasts. Many hypotheses have been put forward regarding the origin of mitochondrial and chloroplast DNA. The generally accepted point of view today is that they are the rudiments of the chromosomes of ancient bacteria that penetrated into the cytoplasm of the host cells and became the precursors of these organelles. Mitochondrial DNA codes for mitochondrial tRNA and rRNA, as well as several mitochondrial proteins. More than 95% of mitochondrial proteins are encoded by nuclear DNA.

STRUCTURE OF GENES

Consider the structure of the gene in prokaryotes and eukaryotes, their similarities and differences. Despite the fact that a gene is a section of DNA encoding only one protein or RNA, in addition to the direct coding part, it also includes regulatory and other structural elements that have a different structure in prokaryotes and eukaryotes.

coding sequence- the main structural and functional unit of the gene, it is in it that the triplets of nucleotides encodingamino acid sequence. It starts with a start codon and ends with a stop codon.

Before and after the coding sequence are untranslated 5' and 3' sequences. They perform regulatory and auxiliary functions, for example, ensure the landing of the ribosome on mRNA.

Untranslated and coding sequences make up the unit of transcription - the transcribed DNA region, that is, the DNA region from which mRNA is synthesized.

Terminator A non-transcribed region of DNA at the end of a gene where RNA synthesis stops.

At the beginning of the gene is regulatory area, which includes promoter and operator.

promoter- the sequence with which the polymerase binds during transcription initiation. Operator- this is the area to which special proteins can bind - repressors, which can reduce the activity of RNA synthesis from this gene - in other words, reduce it expression.

The structure of genes in prokaryotes

The general plan for the structure of genes in prokaryotes and eukaryotes does not differ - both of them contain a regulatory region with a promoter and operator, a transcription unit with coding and non-translated sequences, and a terminator. However, the organization of genes in prokaryotes and eukaryotes is different.

Rice. 18. Scheme of the structure of the gene in prokaryotes (bacteria) -the image is enlarged

At the beginning and at the end of the operon, there are common regulatory regions for several structural genes. From the transcribed region of the operon, one mRNA molecule is read, which contains several coding sequences, each of which has its own start and stop codon. From each of these areasone protein is synthesized. In this way, Several protein molecules are synthesized from one i-RNA molecule.

Prokaryotes are characterized by the combination of several genes into a single functional unit - operon. The work of the operon can be regulated by other genes, which can be noticeably removed from the operon itself - regulators. The protein translated from this gene is called repressor. It binds to the operator of the operon, regulating the expression of all the genes contained in it at once.

Prokaryotes are also characterized by the phenomenon transcription and translation conjugations.

Rice. 19 The phenomenon of conjugation of transcription and translation in prokaryotes - the image is enlarged

This pairing does not occur in eukaryotes due to the presence of a nuclear envelope that separates the cytoplasm, where translation occurs, from the genetic material, on which transcription occurs. In prokaryotes, during the synthesis of RNA on a DNA template, a ribosome can immediately bind to the synthesized RNA molecule. Thus, translation begins even before transcription is complete. Moreover, several ribosomes can simultaneously bind to one RNA molecule, synthesizing several molecules of one protein at once.

The structure of genes in eukaryotes

The genes and chromosomes of eukaryotes are very complexly organized.

Bacteria of many species have only one chromosome, and in almost all cases there is one copy of each gene on each chromosome. Only a few genes, such as rRNA genes, are contained in multiple copies. Genes and regulatory sequences make up almost the entire genome of prokaryotes. Moreover, almost every gene strictly corresponds to the amino acid sequence (or RNA sequence) that it encodes (Fig. 14).

The structural and functional organization of eukaryotic genes is much more complex. The study of eukaryotic chromosomes, and later the sequencing of complete eukaryotic genome sequences, has brought many surprises. Many, if not most, eukaryotic genes have interesting feature: their nucleotide sequences contain one or more DNA regions that do not encode the amino acid sequence of the polypeptide product. Such non-translated inserts disrupt the direct correspondence between the nucleotide sequence of the gene and the amino acid sequence of the encoded polypeptide. These untranslated segments in the genes are called introns, or built-in sequences, and the coding segments are exons. In prokaryotes, only a few genes contain introns.

So, in eukaryotes, there is practically no combination of genes into operons, and the coding sequence of a eukaryotic gene is most often divided into translated regions. - exons, and untranslated sections - introns.

In most cases, the function of introns has not been established. In general, only about 1.5% of human DNA is "coding", that is, it carries information about proteins or RNA. However, taking into account large introns, it turns out that 30% of human DNA consists of genes. Since genes make up a relatively small proportion of the human genome, a significant amount of DNA remains unaccounted for.

Rice. 16. Scheme of the structure of the gene in eukaryotes - the image is enlarged

From each gene, an immature, or pre-RNA, is first synthesized, which contains both introns and exons.

After that, the splicing process takes place, as a result of which the intron regions are excised, and a mature mRNA is formed, from which a protein can be synthesized.

Rice. 20. Alternative splicing process - the image is enlarged

Such an organization of genes allows, for example, to implement when from one gene can be synthesized different forms protein, due to the fact that in the process of splicing exons can be sewn together in different sequences.

Rice. 21. Differences in the structure of genes of prokaryotes and eukaryotes - the image is enlarged

MUTATIONS AND MUTAGENESIS

mutation called a persistent change in the genotype, that is, a change in the nucleotide sequence.

The process that leads to mutation is called mutagenesis, and the organism all whose cells carry the same mutation mutant.

mutation theory was first formulated by Hugh de Vries in 1903. Its modern version includes the following provisions:

1. Mutations occur suddenly, abruptly.

2. Mutations are passed down from generation to generation.

3. Mutations can be beneficial, deleterious or neutral, dominant or recessive.

4. The probability of detecting mutations depends on the number of individuals studied.

5. Similar mutations can occur repeatedly.

6. Mutations are not directed.

Mutations can occur under the influence of various factors. Distinguish between mutations caused by mutagenic impacts: physical (eg ultraviolet or radiation), chemical (eg colchicine or reactive oxygen species) and biological (eg viruses). Mutations can also be caused replication errors.

Depending on the conditions for the appearance of mutations are divided into spontaneous- that is, mutations that have arisen in normal conditions, and induced- that is, mutations that arose under special conditions.

Mutations can occur not only in nuclear DNA, but also, for example, in the DNA of mitochondria or plastids. Accordingly, we can distinguish nuclear and cytoplasmic mutations.

As a result of the occurrence of mutations, new alleles can often appear. If the mutant allele overrides the normal allele, the mutation is called dominant. If the normal allele suppresses the mutated one, the mutation is called recessive. Most mutations that give rise to new alleles are recessive.

Mutations are distinguished by effect adaptive, leading to an increase in the adaptability of the organism to the environment, neutral that do not affect survival harmful that reduce the adaptability of organisms to environmental conditions and lethal leading to the death of the organism early stages development.

According to the consequences, mutations are distinguished, leading to loss of protein function, mutations leading to emergence the protein has a new function, as well as mutations that change the dose of a gene, and, accordingly, the dose of protein synthesized from it.

A mutation can occur in any cell of the body. If a mutation occurs in a germ cell, it is called germinal(germinal, or generative). Such mutations do not appear in the organism in which they appeared, but lead to the appearance of mutants in the offspring and are inherited, so they are important for genetics and evolution. If the mutation occurs in any other cell, it is called somatic. Such a mutation can manifest itself to some extent in the organism in which it arose, for example, lead to the formation of cancerous tumors. However, such a mutation is not inherited and does not affect offspring.

Mutations can affect parts of the genome of different sizes. Allocate genetic, chromosomal and genomic mutations.

Gene mutations

Mutations that occur on a scale smaller than one gene are called genetic, or dotted (dotted). Such mutations lead to a change in one or more nucleotides in the sequence. Gene mutations includesubstitutions, leading to the replacement of one nucleotide by another,deletions leading to the loss of one of the nucleotides,insertions, leading to the addition of an extra nucleotide to the sequence.

Rice. 23. Gene (point) mutations

According to the mechanism of action on the protein, gene mutations are divided into:synonymous, which (as a result of the degeneracy of the genetic code) do not lead to a change in the amino acid composition of the protein product,missense mutations, which lead to the replacement of one amino acid by another and can affect the structure of the synthesized protein, although often they are insignificant,nonsense mutations, leading to the replacement of the coding codon with a stop codon,mutations leading to splicing disorder:

Rice. 24. Mutation schemes

Also, according to the mechanism of action on the protein, mutations are isolated, leading to frame shift readings such as insertions and deletions. Such mutations, like nonsense mutations, although they occur at one point in the gene, often affect the entire structure of the protein, which can lead to a complete change in its structure.

Rice. 29. Chromosome before and after duplication

Genomic mutations

Finally, genomic mutations affect the entire genome, that is, the number of chromosomes changes. Polyploidy is distinguished - an increase in the ploidy of the cell, and aneuploidy, that is, a change in the number of chromosomes, for example, trisomy (the presence of an additional homologue in one of the chromosomes) and monosomy (the absence of a homolog in the chromosome).

Video related to DNA

DNA REPLICATION, RNA CODING, PROTEIN SYNTHESIS