Humans have 23 pairs of chromosomes, and great apes have 24. It turns out (geneticists are increasingly inclined to believe this) that the second pair of human chromosomes was formed from the fusion of pairs of other chromosomes of ancestral anthropoids, as shown in the figure presented at the beginning of the chapter. Here you have 48 pongid chromosomes versus 46 humans! Paris Conference of Genetics and 1971 and 1975 approved a very clear table of homology between the chromosomes of humans and the three great apes. It shows: the chimpanzee is our closest relative with a karyotype almost the same as ours (the dwarf chimpanzee is especially close to us in terms of chromosomes).
But one should not think that other monkeys, including lower ones, are very distant from humans in chromosome structure. Many marmosets, some callicebuses, uakari, even the wari lemur have the same number of chromosomes as humans - 46 (double set); in capuchins - 54; for howler monkeys - 44-52 (different species); in monkeys - from 48 to 72; in macaques and baboons - 42; in langurs - 44; most gibbons have 44 (siamangs have 50). But the relatedness of primates is assessed, of course, not only by the number of chromosomes. If you “stretch” all the chromosomes of each species into one line, it turns out to be the same length in all primate species. Only the number of centromeres (i.e., actually the number of chromosomes) and the distribution of arms change. They also have the same total amount of the substance of heredity - DNA.
In the 60s A great similarity between the karyotypes of humans and many species of lower apes has been established. When studying the phylogeny of chromosomes of 60 species of primates from the mouse Microcebus to humans, the French geneticist B. Dutrillot (1979) established a complete analogy, approximately 70% of non-repeating colored bands. Evidence of close similarity and relationship is also provided by “human” genetic diseases in monkeys: Down syndrome, alkaptonuria, developmental anomalies. The histocompatibility complex (tissue affinity necessary for organ transplantation) is localized in genes on the chromosomes of chimpanzees, gorilla, orangutan and rhesus macaques in the same way - the coloring of these areas in monkeys is completely identical to the pattern on human chromosome 6. The genes “responsible” for encoding five vital enzymes in the capuchin are located on chromosomes 2, 9 and 15 - they are encoded in the same way in human chromosomes that are identical in structure, but have a different numbering.
But, of course, the greatest similarity of chromosomes has been established in humans and chimpanzees - it reaches 90-98% (according to different authors). It is interesting to remember: two species of monkeys, representatives of the same genus - the Brass monkey (diploid set of chromosomes 62) and the talapoin monkey (54 chromosomes) turn out to be homologous in only 10 pairs of chromosomes, i.e., significantly less related than humans and chimpanzees.
Now, after considering the main, fundamental signs of similarity between humans and monkeys based on chromosomes, the relatedness of primates will also be clear based on other indicators related to genetic relatedness. As we remember, genes and their container - chromosomes - are sections of nuclear (that is, nucleic) acids present in each cell, more precisely, deoxyribonucleic acid (DNA). Already in the 60s, immediately after the great discoveries of the 50s. XX century, when the role and structure of DNA was established, its intensive study and comparison in different organisms began. So, we learned to hybridize DNA different types. If you heat it up, it, normally double-stranded, “unwinds” into single strands, onto which you can “grow” (superpose) the same strand of DNA from another animal, if it has similar genes. When these threads cool, they will curl back into a double common spiral, but only to the extent that the organisms that host these two DNAs are related.
It turned out that the DNA of humans and birds hybridizes by 10%, humans and mice by 19%, humans and larger mammals by 30-40%, but humans and rhesus macaques by 66-74%.
As for chimpanzees, here, as mentioned, the hybrid with human DNA reaches, according to various authors, up to 90-98%. The temperature at which this spliced DNA “melts” (it is different for hybrids of different affinity and therefore is also an indicator of the relationship of their owners) fully confirms the special closeness of humans to other primates.
When the rapidly evolving DNA of non-nuclear cell formations - mitochondria - was discovered, skeptics expressed doubts about the reliability of the data obtained based on comparisons of nuclear DNA (although it is well known that it is the main material of chromosomes, localized, as they say, in the nucleus of the cell): after all, DNA mitochondria, according to some authors, changes 5-10 times faster than the nuclear one and, thus, presents us with genetic changes as if in an enlarged form.
Californian biochemists conducted a study (Alan Wilson, already known to us, participated in it) specifically to study mitochondrial DNA. The method they used is extremely accurate. It is based on identifying DNA regions that are cleaved by highly specific enzymes - restriction endonucleases. These enzymes recognize strictly defined sequences of DNA nucleotides and cut the molecule only in these places. As a result, even minor changes in the composition or order of nucleotides become available for analysis.
By constructing maps of sites (or, as scientists say, sites) of the action of various restriction enzymes, it is possible to analyze very closely related DNA molecules, for example, subtypes of the same virus, etc. And still the same result - extraordinary relatedness! And to the same extent, which has been established by biochemical and genetic methods already known to the reader, chimpanzees and gorillas are as close as possible to humans. Further away is the orangutan, and a little further away are the gibbons.
The same conclusion was made when studying the “satellite” DNA of chromosomes, when mapping the interferon gene family, etc.
After such a great similarity in chromosomes (DNA), no one can be surprised by the “striking” similarity of blood proteins and tissues of humans and monkeys - after all, they, proteins, receive a “program” from parental substances that encode them, so close, as we have seen , i.e. from genes, from DNA! Proteins are mainly now studied, along with immunological methods, by determining the sequence of amino acids, the order and alternation of which, as it also became known in the 50s, constitutes the “physiography” of each protein.
We have already seen the level of similarity between the albumin protein in humans and various animals. In general, it is detected in approximately the same sequence for other proteins, but sometimes it is higher - according to these indicators, African anthropoids are closer to humans. Here are the data on transferrin - immunological similarity is expressed as a percentage as follows: in humans with chimpanzees and gorilla - 100% (complete identity!), with Old World monkeys - from 50 to 75, with other animals - either below 4% or zero, lack of similarity. Professor G. A. Annenkov quite reasonably assumed that " high degree identity in structure and function extends to many serum proteins in the blood of all (or most) primates."
And here is the data on low-density lipoproteins, which play a crucial role in the development of atherosclerosis: their immunological similarity in humans with reptiles and fish is 1-10%, with birds - 10, with pigs - 35-58, with various narrow-nosed monkeys - 80-85 , with chimpanzees - more than 90%. Another related blood component, apolipoprotein, also according to immunological studies, is homologous in humans and various monkeys, but is indistinguishable in the plasma of humans, chimpanzees and gorillas.
The similarity between humans and monkeys in the structure and properties of many hormones is incomparable with any other animals. Growth hormone is very species specific, but is the same in humans and even macaques. Introduced to a child from monkeys, it will act as effectively as the same hormone from humans (it has been established Nobel laureate American Lee Cho Hao). Almost complete identity was established recently (Wethekham et al., 1982) when studying the nucleotide sequence of DNA encoding the hormone insulin in humans and cynomolgus monkeys; in the hormone itself, in its protein, only two substitutions in the amino acid sequence can be found.
As Sukhumi endocrinologists N.P. Goncharov, G.V. Katsia, V.Yu. Butnev showed, there are no animals in nature as close to humans as monkeys, in particular baboons, in terms of the nature of the exchange of steroid hormones produced by the adrenal glands and playing a colossal role role in the reproductive system. Mice, rabbits, and rats, which, I note, are constantly used in studies of steroidogenesis, produce the hormone corticosterone in the greatest quantities, while in humans and monkeys the predominant hormone of this group is cortisol. The ratio of the two named hormones in both primates is almost the same and is strikingly different from their proportions in rodents.
Translation: Vladimir Silenok
Editing: Anna Nebosova
Image iStockphoto
Do humans and chimpanzees have a common ancestor? Is there genetic evidence that our species are related? Where would we turn if we wanted to check this? There are many suitable ranges in the genome, but new data on the chimpanzee Y chromosome could easily shake them off the evolutionary genetic tree!
According to many evolutionists, the Y chromosome—the DNA sequence that makes men who they are—is likely a degenerative remnant of our evolutionary history. It is dense, small and slightly curved in shape; most of it consists of repetitive material. It contains relatively few protein-coding genes. Since the corresponding X chromosome is much larger, it was generally accepted that the Y chromosome does not perform essential functions. In addition, only part of the Y chromosome is different from the X chromosome (the SRY gene).
Humans and chimpanzees are very different, as can be seen from comparing their Y chromosomes. (Photo: Photo iStockphoto)
Add to this the views of modern feminism, which disdains everything related to men, and you have every reason to throw the Y chromosome into the dustbin of history. One paper published in 2009 (coincidentally, written by two women) concluded that there had been enormous gene loss on the Y chromosome of placentals, and that the Y chromosome would eventually disappear altogether if this the loss will continue. Of course, such conclusions are based on the belief that the X and Y chromosomes were once identical (after all, there are two copies of all chromosomes), and that the Y chromosome is not a “design feature.” Those who come to such conclusions ignore the fact that every member of the placental genus still has a Y chromosome. They should have concluded that this Y chromosome must be very important, because in the last 100 million years or so (using their dating scheme) it has not been lost by any species of placental mammals. However, they drew conclusions based on false initial premises and considered the Y chromosome to be vestigial. This is just one of many examples that describe this new modern trend.
In reality, this trend is wrong. Based on modern genetics, we learn that the Y chromosome is the master control switch that influences the expression of thousands of modern genes found on all other chromosomes. Her influence is so deep that she is responsible for the differences between men and women. The Y chromosome is also very important for the study of heredity and evolution due to the fact that it is directly inherited from the father. Using data obtained from Y chromosome sequencing, a genetic tree of Y chromosomes can be constructed and used as a graph of migration patterns in people around the world. It was previously discovered that all men have a very similar Y chromosome. This naturally suggests the conclusion that there was one male ancestor for the entire world population, called the Y-chromosomal Adam.
New research on the chimpanzee Y chromosome has surprised many. As a result of the work done, the Y chromosomes of chimpanzees were finally deciphered. This may come as a surprise to all those who thought that the chimpanzee genome was completely sequenced back in 2005. In fact, the structure of the original chimpanzee genome was unsatisfactory because it was not sequenced to the same standards as humans. On the contrary, the human genome was used as a “scaffold” for the reconstruction of the chimpanzee genome. This led to several problems, the worst of which was repetitive sequences. There are significant differences between the repeat ranges of the human and monkey genomes, and due to the fact that the Y chromosomes have extremely repetitive in nature, the chimpanzee version of the genome was essentially left unfinished. Today, even the human Y chromosome is only half deciphered. The chimpanzee Y chromosome was left in a much worse state, but recent work has largely corrected all previous deficiencies.
Due to the fact that the Y chromosomes small size And supposed that they evolved from larger chromosomes, then allowed that evolutionary history includes loss large quantity genes. However, the paper reaches a different conclusion because its authors found striking differences between humans and chimpanzees, including radical differences in the sequence of gene content corresponding to the SRY ranges. Given these vast differences, the researchers concluded that chimpanzees have lost many SRY-coding genes, including entire gene families, as we presumably descended from the last common ancestor. These are significant changes. According to David Page, who sequenced the human genome, the two chromosomes are "... strikingly different from each other... There appears to have been a radical rearrangement or reworking of the Y chromosome in the human and chimpanzee lineages."
What are these differences? There are two main classes of SRY sequences common to both species: “amplicon” and “X-degenerate” (humans also have “X-transposed” sequences, which are not found in chimpanzees). The X-degenerative ranges between chimpanzees and humans differ by as much as 10%. This is a huge difference considering the “99% identity” claim that has been made so often over the past few decades. But this is where the differences just begin. In order to compare amplicon ranges, we had to talk about full-scale rearrangement and “rampant” loss and acquisition of sequences. Half of the amplicon sequences and 30% of all SRY in chimpanzees have no copy in human SRY and vice versa. These are very noticeable differences.
The 30% difference between the SRY ranges of humans and chimpanzees was quite a shock. A similar degree of difference would be expected between the euchromosomes of a human and something like a chicken, even though the chicken is not even a mammal. The discovery of so many differences in one of the sex chromosomes was of great significance. Taking a look at the genetic makeup of the two corresponding chromosomes, the researchers were also surprised to find much more in the chimpanzee genome. fewer genes than in humans—“only two-thirds the distinctive genes or gene families, such as human SRY, and half as many protein-coding transcriptional units.” They saw a huge difference in the number and type of genes on the two Y chromosomes and were forced to argue that an evolutionary process was responsible for the huge loss or gain of genes. Of course, intelligent design was not considered a likely answer.
Explaining their findings, they proposed several factors that contributed to the differences between chimpanzees and humans, including sperm competition (because less DNA per cell is presumably an advantage for male chimpanzees, since lighter sperm can out-compete heavier sperm) , “genetic hitchhiking” (when harmful mutations are carried along with positive ones) and high rates of gene conversion (when similar sequences recombine inside chromosomes, leading to sequence homogenization). Again, intelligent design was not considered to be the cause of these differences.
The idea that the Y chromosome evolves at a rapid rate is based on the assumption of a common ancestor. But there is an extremely low level of variation among human Y chromosomes, which would not be expected if they mutated at a tremendous rate, so there is no real evidence of evolutionary changes in these chromosomes. Most of sequences belongs to the Y chromosome of a single male, but we do not know how exactly they differ from each other.
So what conclusion can we draw based on the information presented here? First, for evolutionists, this means that the Y chromosome appears to be evolving much faster than ever imagined (in evolutionist parlance, “evolving faster” means “very different”). They will now have to use mathematical models to try to demonstrate how incredibly quickly sequences can change (including rearrangements of entire gene families in a relatively short period of time) while at the same time remaining homogeneous within a species. They have a very difficult task ahead of them.
Secondly, for creationists, this means that the old adage that “humans and chimpanzees are 99% identical” is hopelessly outdated. Interestingly, back in 2007, a compelling article appeared calling the 99% rule a “myth” and stating that it has been known for decades that humans and chimpanzees are very different from each other. But this statement was an impressive and serious argument in defense of evolution. How many people have been "shipwrecked" when their faith was shattered on these "mythical" rocks? We now have half of the chimpanzee's Y chromosome at our disposal, and we understand that it is only 70% identical to humans. This is proof that humans and chimpanzees are very different from each other. How different are they? Here's what the famous geneticist Svante Pääbo says about this: “I don’t think it’s possible to calculate an exact figure... In the end, how we see our differences is a political, social and cultural issue.” This statement was made even before data on the Y chromosome became available to the public. If it's impossible to make an accurate calculation, isn't it time for us to throw everything overboard? evolutionary stories about common ancestors between humans and chimpanzees? New data on the Y chromosome of chimpanzees makes a compelling case, greatly complicating the question of the existence of a common ancestor.
Links and notes
1. Wilson, M.A., and Makova, K.D., Evolution and survival on eutherian sex chromosomes, PLoS Genetics 5(7):e1000568, 2009. See also http://www.physorg.com/news167026463.html.
2. Hawley, R. S., The Human Y Chromosome: Rumors of Its Death Have Been Greatly Exaggerated, Cell 113:825–828, 2003.
3. Lemos, B., et al., Polymorphic Y chromosomes harbor cryptic variation with manifold functional consequences, Science 319:91-93.
4. 598-612, 2003.
5. Jobling MA, Tyler-Smith C., The human Y chromosome: an evolutionary marker comes of age. Nature Reviews Genetics 4:598-612, 2003.
6. Batten, D., Y-chromosome Adam? TJ 9(2):139–140, 1995.
7. Hughes, JF, et al., Chimpanzee and human Y chromosomes are remarkably divergent in structure and gene content. Nature 463:536-539, 2010.
8. Buchen, L., The fickle Y chromosome, Nature 463:149, 2010.
9. Cohen, C., Relative Differences: The Myth of the 1%, Science 316:1836, 2007
Chromosomes are a nuclear structure that carries embedded genetic information in the genus of genes (DNA). Geneticists are studying this direction and know how many chromosomes does a monkey have, how much does a person have and .
DNA contains hereditary data intended for transmission and storage. Everyone knows from school biology courses that humans have 23 pairs of chromosomes, making a total of 46. Some believe that monkeys and humanity are not far from each other in development.
The strangest thing is chimpanzees have 48 chromosomes, only two less than a human. There is a study proving that in the process of human evolution, a pair of diverse chromosomes became one chromosome. How does this happen? Read on.
In the 70s of the last century, the similarities between human and monkey chromosomes were studied. Primatologist Friedman wrote that the difference in the nucleotide chains of the gene sequence between chimpanzees and humans was 1.1%.
A little later, in the 80s, one very popular magazine called “Science” published an article from a group of geneticists at a university in Minneapolis. At that time, scientists used new technologies for studying chromosomes.
Geneticists stained chromosomes, and transverse stripes of varying brightness and thickness appeared on them, and each chromosome showed its own individuality and uniqueness, because it had its own set of such stripes.
As you probably already understood, the chromosomes of humans and monkeys were “distributed”. Studies have shown that we have the same striations! What about the extra chromosome?
The fact is that if you look opposite the second chromosome and imagine the twelfth and thirteenth monkey chromosomes in one line, then putting their ends together, it turns out that together they form the second human chromosome.
There is further evidence that a pair of chromosomes was once missing in humans. They conducted another experiment in the 90s, which showed that if you look at the point of supposed unification on the 2nd human chromosome, scientists saw that the DNA has a terminal section of chromosomes that are characteristic of the so-called telomeres.
It has been confirmed that it is the number of chromosomes that sets the boundaries between species, and it is this number that prevents further hybridization and change in species. When scientists began to study the karyotypes of various mammals, they discovered that the number of chromosomes varied!
For example, Rogacheva and Borodin noted that at different territorial sites the same animals different quantity chromosomes! So, for example, the shrew living in Sri Lanka has fifteen pairs of chromosomes (thirty in total), and in Arabia - twenty pairs of chromosomes (forty in total). As it was discovered later, several chromosomes became smaller because chromosomes merged.
It turns out that if during meiosis, and this is cell division during which new germ cells are formed, each chromosome must unite with its homologous pair. IN human body one chromosome turns out to be unpaired.
Borodin's theory
The same scientist Borodin, mentioned above in the article, says that he himself conducted some experiment that confirms this theory. Borodin checked that the so-called Punare (rat) had twenty-nine chromosomes. Why did this happen?
It turns out that there was a crossing between two populations of rodents that had thirty and twenty-eight chromosomes. Borodin wrote: “The three chromosomes that remained formed a trio of chromosomes.
On one side there is a long chromosome that came from the twenty-eighth parent, and on the second side there are two much shorter chromosomes that came from the thirty-chromosomal parent.
It turns out that all the chromosomes have found their place.” Here is the material on the topic: how many chromosomes does a monkey have.
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 mass culture, and pseudo-scientific ideas that exist among educated and well-read people. Do you want to know how everything “really” was? Alexander Sokolov, Chief Editor 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 between two neighboring rooms broke the wall. It turned out to be 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 interbreed? different numbers chromosomes?
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"
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