Scientists, in the majority, people cultural, humane. They try to present their discoveries to the public in such a way that the public is not frightened. For example, they will invent nuclear weapons capable of destroying all life in vast territories in a matter of moments, and they will present it to us as “work on the study and use of a nuclear chain reaction.” The same thing happens with horizontal gene transfer. Under this, obscure to the uninitiated and absolutely frightening term actually hides a real genetic terrorism.
Yes, terrorism! And what else can you call the forced and secret introduction of foreign genes into our body? Okay, if you don’t want terrorism, let it be “genetic banditry,” not “horizontal gene transfer.” When people hear about some kind of “gene transfer”, they do not understand how this transfer is terrible for them. But the words ” terrorism “or” banditry ” make you wary and look for ways to protect yourself.
That’s the way it is! That is, not in them, but in their absence! Scientists do not know how to protect themselves from the gangster genetic terrorism of microbes, how to prevent them from introducing their genes into our body. They are invisible to the naked eye, they are billions and they are everywhere. Here you are now calmly reading this book and do not feel like you quietly “insert” the gene of some amoeba or Clostridium… what, calmness has evaporated somewhere? That’s it!
The fact that scientists have not yet discovered ways to protect against microbial genetic terrorism does not mean that this protection does not exist at all. Let’s hope that soon things will move forward and we do not have to fear that we can suddenly turn from a multicellular organism into a collection of different unicellular organisms. What did you think?” Genes are the bedrock! Genes are information! Why do you think insidious microbes introduce their genes into our cells? Do they have nothing else to do or just a hobby they have? No, not a hobby, but an instinct! And calculation! Just multiply by dividing, it turns out slower than sharing and passing on their genes in the wrong cells to implement. Every microorganism strives to become the only inhabitant of our planet. Such is their, germs, dream and life-changing goal.
Viruses are particularly zealous in this regard. They are as long as your in the cell the gene is not embedded, cannot live and reproduce. So behave all viruses without exceptions. Now count how many times you have had viral diseases…
Knowing about such a great danger, it is impossible to sit idly by.
But what can we do?
Try to have as little contact with germs as possible?
Alas, this is impossible. They are everywhere, including within us…
How awful!
Horror-horror-horror-horror-horror!
No, you can still do something productive.
Take a fork and once again remove from your real ears conditionally-imaginary noodles. That’s one.
Acquire minimal knowledge of genetics, so that the word “genes” on your body would not start to run goosebumps. That’s two.
Call things by their real names. That’s three.
Look at the root! That’s four.
Now, a course in genetics that is required to debunk the myth that gangster genetic terrorism microbes. Or about the genetic terrorist banditry. It is possible to call this business and “robbery”, the paper, as we know, will endure everything. But it is better to call it horizontal gene transfer. Remember that horizontal gene transfer is the process by which one organism transfers genetic material to another organism that is not a descendant of the first. The transfer of genes from ancestors to descendants is called vertical transfer.
Every cell needs the instructions of life – growth, reproduction, etc. in other words, we need information. This information, called hereditary, daughter cells receive from the mother, and multicellular organisms-from their parents. Unicellular organisms, formed as a result of sexual reproduction (there are unicellular and such), also receive hereditary information from both parents.
Hereditary information is recorded in the molecules of deoxyribonucleic acids, known to everyone (well, at least from the series) under the abbreviation DNA. DNA is a giant double-stranded molecule made up of four types of fragments called nucleotides. The number of nucleotides can reach several hundred million. For compactness, the DNA molecule consists not of one, but of two chains, which in addition are twisted around its axis in a spiral, forming something resembling a double spring. The chains are held together by “bridges” consisting of atoms of carbon, oxygen, hydrogen, nitrogen and phosphorus.
The combination of four nucleotides is a kind of” cipher”, which” encrypted ” information. The portion of DNA that encodes one single feature of an organism is called a gene. A gene is not a single molecule or a group of molecules, but a single section of a giant DNA molecule.
The chains that make up DNA molecules can break and reconnect. Nature has provided for such a possibility, the details of which we will not delve, because we do not need it now. We need to understand that these chains can be broken, inserted into the “foreign” areas (ie, other people’s genes) and” sew ” again. And you can not paste and cut… And another similar (a pair) of the DNA molecule can exchange sites with each other.
A chromosome is a single DNA molecule in combination with certain proteins, which, to put it crudely and simply, act as a “package” for the DNA molecule. The chromosomes themselves,” Packed ” together and compactly, form the cell nucleus.
In nuclear-free cells, chromosomes as such do not exist. For example, in bacteria, a single DNA molecule is not “Packed”, but simply closed in a ring. A complex of a “ring” DNA molecule with proteins and some other substances is called a nucleoid. The expression “bacterial chromosome” is not quite literate, however, is often used in the scientific literature consciously, because, what is the chromosome, represent all (well, at least remotely), and about nucleoids no one except biologists and physicians, has no idea.
In bacteria, in addition to the nucleoid (main DNA), there are smaller DNA molecules, rolled into a ring and scattered in the cytoplasm. Such complexes are called plasmids.
Plasmids are able to double independently, outside the process of cell division, in other words-are capable of Autonomous reproduction. However, unlike viruses, which because of the ability to reproduce part of scientists are considered as living organisms, plasmids are considered a cellular component, organoid. Although if you think about it, the essence of viruses and plasmids is the same – DNA in protein packaging. Plasmids usually contain genes that increase the fitness of bacteria to the environment. On the basis of information contained in these genes produced proteins that make bacteria more resistant to adverse environmental factors (for example, antibottom).
Eukaryotic cells also have structures that have their own DNA, that is, “personal” genetic information. These are mitochondria and chloroplasts.
Mitochondria are a kind of energy station cells, which are subjected to oxidation of organic substances entering the cell from the outside. In the process of oxidation, adenosine triphosphate (ATP) molecules are formed, accumulating energy in their chemical bonds (a kind of cell batteries). Typically, a cell contains about two thousand mitochondria. Mitochondria are spherical or ellipsoidal in shape.
Mitochondria are present in both animal and plant cells, and chloroplasts or green plastids are present only in plant cells. Chloroplasts carry out photosynthesis. Due to the presence of DNA, mitochondria and chloroplasts independently synthesize a number of proteins, so they are referred to as semi-Autonomous cell structures. Other proteins in the cell are synthesized based on information encoded in the main DNA contained in the nucleus.
Between plasmids and mitochondria with chloroplasts there is one significant, we can say – a fundamental difference. Bacteria (including bacteria of different species) can exchange plasmids with each other, that is, share genetic information with each other. But mitochondria and chloroplasts eukaryotic cells do not exchange with each other. “Autonomy” of mitochondria and chloroplasts is limited by the ability to independently synthesize some proteins.
In addition to DNA, there are also RNA-ribonucleic acids, which differ from DNA molecules in chemical structure and size. RNA molecules are much smaller than DNA molecules. They are single-stranded or are numerous short fragments collected in something like a ball.
Like DNA molecules, RNA molecules are made up of four kinds of nucleotides. In DNA-containing organisms, different RNAS perform different functions – to serve as matrices for the synthesis of molecules of various proteins, to transport substances inside the cell, to start the synthesis of a daughter molecule of deoxyribonucleic acid on the matrix of the parent molecule [23]. And some viruses that do not have DNA, hereditary information is recorded in RNA.
It is necessary to make one clarification. Do not think of a four-nucleotide code as a four-digit combination from 0000 to 9999. No, the DNA code is a long series consisting of four coding elements: “…123234432113214412341…” the number of elements in the series is not limited and combinations of options here can be infinitely many.
At the end of our short course of genetics, let’s remember about viruses, which differ from living organisms by a complete lack of metabolism, as well as the absence of cell structure and protein synthesis apparatus. But at the same time, viruses have genetic material, are capable of reproduction (even inside the host cell) and evolve by natural selection [24], which allows them to be attributed to living organisms. Through its nucleic acid (DNA or RNA), the virus controls the host cell and programs its systems to synthesize its viral material (nucleic acid and viral envelope proteins) from the host cell substances. We can say that the virus “subordinates” the cell and shamelessly uses its resources.
All! The short course in genetics is over. You can consider yourself geneticists of the first Dan, with whom you can have a Frank conversation on a professional level.
Can organisms that are not parents and descendants, including organisms belonging to different species, exchange genetic information among themselves?
Yes-can! Horizontal gene transfer actually exists in nature.
Does this horizontal gene transfer threaten us?
It’s threatening, it’s threatening!
Horizontal gene transfer enables bacteria to share antibiotic resistance with each other, and this resistance is today the leading problem in the treatment of diseases caused by infectious agents and one of the leading problems of modern pharmacology. Figuratively speaking, we with pathogenic microbes are in a state of incessant “arms race”. As soon as we hit the microbes with a new antibiotic, they immediately begin to build defenses – to develop resistance to this drug. We have to create a new antibiotic, which immediately… You know. Not only are microorganisms able to produce this resistance, they can also share it, through the exchange of plasmids.
It is the exchange of plasmids between cells and provides horizontal gene transfer in bacteria. Two bacteria come together, at the site of contact of their cell membranes are destroyed, the exchange of plasmids, then the membranes are restored and the bacteria diverge. Simple, fast, convenient, effective. But it is possible to exchange plasmids and even easier-without fusion. One bacterium “throws out” the plasmid, that is, displays it in the external environment, and the other – takes the “orphan” plasmid itself.
If you have a restless heartbeat, cold hands and hair stood on end, then take a few deep breaths, drink water or something else calming, and then read on.
We have no reason to worry, because there is no “genetic terrorism”. Exchange of plasmids is possible only between bacteria and only in prokaryotic (nuclear-free) bacterial cell plasmids can function, that is, provide protein synthesis based on the information contained in their plasmid DNA.
It must be said that the human consciousness is arranged in the most amazing way. We all know that a part from a car of one brand is likely not suitable for a car of another brand, that the remote control of the air conditioner can not control the TV and that one key can not open all the locks. But at the same time, most of us think that all living cells are the same. Thinks, despite the variety of wildlife every day flashing in front of us.
If mushrooms and Hydra reproduce by budding, it does not mean that cheetahs and hamadryas should also multiply in this way. Despite the fact that their names also begin with the letter “g”. Something like that.
A bacterium can transfer its plasmids to another bacterium, but cannot transfer them to cells of the colon mucosa or, say, the vaginal mucosa. Even artificially it can not be done. To the great chagrin of genetic engineers, who are engaged in the transfer of genes from one organism to another. If you attach a gene to a plasmid, the plasmid can act as its carrier between bacteria, since bacterial cells readily absorb foreign plasmids. But plasmids, unfortunately, will not help to introduce someone else’s gene in plant cells or, say, in animals.
Sorry? What the hell kind of regret? Fortunately! Fortunately!
Sleep well and live without fear. Under no circumstances, no matter what side to you would not turn fortune, you are not in danger of turning from the crown of creation in a crowd of heterogeneous bacteria. It will never happen, because it cannot happen. The myth of the possibility of gene exchange between bacteria and humans arose due to the incorrect distribution of the identified features of bacterial cells to all living organisms without exception. You can’t do that, even if you really want to, because it’s unscientific.
Unscientific, but tickles the nerves efficiently. Just imagine your leg (or arm, whatever) turned into a bunch of bacteria, like… okay, enough of the scary stuff. We have a popular science book about Microbiology, not horror in stephenkingrocks spirit.
Now some readers knowingly smile and think:”Yes, enough to fool us with bacteria and plasmids, let’s talk about viruses.”
Let’s talk. This is what we were going to do, because without the viruses that genetic engineers use to transplant genes, the topic of horizontal transfer would not be fully understood.
Yes-viruses alter the DNA of the cells they invade. That is, in fact, “switch” the attention of cells to their DNA or RNA. Normally, a cell lives by the laws (or codes) established by its DNA. In DNA everything is spelled out thoroughly-when and in what quantity what protein to synthesize. Any sign of a living organism is determined by those or other proteins, synthesis which encode genes.
The virus gives the cell its nucleic acid and in some unfathomable way “diverts the attention” of the cell from its own cellular DNA. As soon as scientists establish the mechanism of this “distraction”, the viruses will be in trouble, because they will never be able to infiltrate anywhere. Who knows the mechanism of the process, he will always find an opportunity to counteract this process.
Simplistically and roughly we can say that the virus replaces the DNA of the cell in which it parasites. This is not a horizontal transfer of genes in a pure and unclouded form, but something identical, close-foreign genes penetrate into the cell and the cell begins to read the information inherent in them.
What’s the danger?”
Or cell death and the increase in the number of viruses that managed to “stamp” a cell before his death, or changing the properties of cells, for example – the appearance of abnormal abilities to uncontrolled reproduction, i.e. cancer process. But no virus is able to turn the affected organism (unicellular or multicellular) in its likeness. It can only reproduce by parasitizing the cell. That’s why in the case of viruses they don’t talk about horizontal gene transfer. True horizontal transfer takes place only when the cell that received the genetic material, uses it in the process of its normal life and transmits it to offspring – daughter cells.
Necessary clarification-the above-mentioned ability of cells to reproduce uncontrollably, caused by a virus, is not a consequence of the” exploitation ” of viral DNA or RNA, and the consequence of changes in the cell DNA caused by the virus. Here we are not dealing with horizontal gene transfer, but with mutation-a persistent structural change in genetic material (genes), which leads to a change in hereditary information. The word “persistent” means that this change can be inherited by descendants. A mutation is a “side”, so to speak, the action of the virus.
It is necessary to know that the cells of multicellular organisms that reproduce sexually, are divided into somatic (normal) and sexual. Sex cells are used for reproduction. They contain half a set of chromosomes (DNA). Each descendant organism receives half of its DNA from its father and half from its mother. But somatic cells also produce offspring. They reproduce by ordinary division. Almost all cells of our body, except for part of the brain cells, are constantly self-renewing-some die, others come to replace them. Conditionally-approximately it is possible to tell that for seven-eight years our organism is completely renewed. This is so, for the record, as a Supplement to a short course in genetics.
There would be a hypothesis, and proofs to it will always be tightened. More precisely-will be tightened. Those readers who are seriously interested in the topic of horizontal gene transfer, can remember what they have read about examples of this transfer almost our “relatives”, the apes.
Yes, there were such messages. After the discovery of horizontal gene transfer between bacteria, scientists began to look for something similar in host-parasite systems. Why there? Because with so close, so close contact between individuals of different species, the possibility of horizontal gene transfer seemed most likely.
The hypothetical mechanism of gene transfer from the parasite to the host is something like this-when the parasite drinks the host’s blood, some of its cells enter the host’s bloodstream, spread throughout the body and, eventually, can be absorbed by the host’s cells. Actually, the cells of the immune system are responsible for eating aliens and then digesting what they eat, but we can assume that some cells, or at least their DNA, can be absorbed by nonimmune cells. Parasite DNA “take root in a new place”, that is, embedded in the cell DNA, at least not completely, and fragmentary. Here you have a horizontal shift. Maybe some of the cells of the host, once ingested, the parasite drinking blood, “enrich” it with my DNA…
Theoretically, such a process is possible, but practically-not very much. In any case, it has not yet been discovered and described. Openly, indeed do-detected similarity between individual genes some parasites and their hosts. For example, the blood-sucking bug of Rhodnius prolixus living in South and Central America, and squirrel monkeys, in which this bug is a parasite. Please note – open mechanism of gene transfer from bugs to apes (or Vice versa) and not even any “hints” on the mechanism, but only a similarity of separate and smaller sections of the DNA of the bug and the monkeys. Similar DNA fragments were also found in certain rodent, possum, lizard and frog species.
What can be said about this similarity?
Absolutely nothing.
Now, if the crime scene find a cigarette butt with the fingerprints and the remnants of saliva is known recidivist, it still gives rise to some preliminary conclusions. Considering the cigarette butt could have been planted … we need to figure it out. But the similarity of individual fragments of different DNA, if you think about it, no reason to conclude does not. Simply put, there is nothing to deal with.
DNA molecules are huge and when comparing the DNA of organisms of different species, you can always find some similar areas. As they say, he who seeks will always find. If you take a person’s DNA and compare it with any other DNA, several similar sites will certainly be found. On the one hand. On the other-a similar similarity is not only possible, but also expected, if we assume that all life on our planet came from a common ancestor – a certain cell-foremother.
Summary
Today (Oh, this eternal reservation, without which it is impossible to do) open and partially studied the process of horizontal gene transfer between bacteria. In multicellular eukaryotes, to which we belong and you, nothing like this has not yet been discovered. To infer the existence of horizontal transport on the basis of the similarity of DNA fragments in organisms belonging to different species (as well as classes, etc.) is like inferring the rotation of the Sun around the Earth on the basis of personal observations. We see with our own eyes every day how this very Sun rises in the East and sets in the West, we see how it moves across the sky, but in fact it is our planet that rotates around the Sun and around its axis. And our planet is round, although the “by eye” it seems as if it is flat. That’s it.
Sleep well, dear friends! Your microorganisms do not encroach on the integrity of your genotype (so, scientifically, called the totality of all the genes of a particular organism). Microbial genetic terrorism-banditry does not exist, it was invented by mythmakers.
He was wrong who first said, “The less you know, the more you sleep,” and those who repeat it are wrong. He sleeps best who knows more, because the more one knows, the less myths poison or burden one’s life. Knowledge is not only strength, but also serenity.