Hybrid creatures fascinated Darwin all his life. The fact that closely related species are able to produce common offspring, possessing the characteristics of both, but usually unable to reproduce and pass these characteristics on to a third generation, was in his view further proof of the theory that the species are gradually drifting apart.
Hybrid creatures fascinated Darwin all his life. The fact that closely related species are able to produce common offspring, possessing the characteristics of both, but usually unable to reproduce and pass these characteristics on to a third generation, was in his view further proof of the theory that the species are gradually drifting apart. Now, 200 years after Darwin's birth, scientists at the Weizmann Institute of Science are examining, using hybrid organisms, what makes one species different from another and what happens in hybrids.
Darwin had not heard of genes when he proposed the theory of evolution in his book "The Origin of Species". Now, after deciphering the genetic code, it turns out that genetic mutations are only responsible for some of the differences between the sexes. Most of the differences arise from the way in which these genes are expressed - "called" - to create the proteins they code for. How do these differences develop in evolution?
Prof. Naama Barkai from the Department of Molecular Genetics, Prof. Avi Levy from the Department of Plant Sciences, and research students Itai Tirosh and Sharon Richav, found that one way to study the differences between two species of yeast is to unite their genetic material together, and create a hybrid yeast, i.e. a hybrid. The findings of their research were recently published in the journal Science.
As in human cells, hybrid yeast cells have two sets of genes ("alleles"), one from each parent. Which of the DNA sequences that play a role in gene expression will be different between different hybrids, and where are they located in the genome? Are they physically associated with the gene ("cis"), like the initiating segments ("promoters") that act as genetic activation switches? Or are they located in a distant place in the genome, and influence it ("trans")? Using a technique they developed to identify the expression of individual alleles, the scientists examined expression patterns in the hybrids, and compared them to those of their parents. When the differences between the parents were preserved in the hybrid yeast, the scientists concluded that the differentiating factor is physically related to the affected gene ("cis"). These factors only affect the allele to which they are linked. But, if the expression patterns were different from parent to parent and became identical in the hybrid yeast, the scientists concluded that the "trans" factors, located elsewhere in the genome, are responsible for the difference (these factors affect both alleles alike).
The scientists found that "cis" type factors physically related to the affected genes underwent more evolutionary changes: they were responsible for more differences in gene expression processes, compared to factors located far from the affected area ("trans"). "Ciss" type factors were apparently not affected by the way the yeast was grown. In contrast, the "trans" elements were sensitive to the environment in which the yeast grew (significant differences were evident between growth in good conditions and growth in distressed conditions). It was also found that the "trans" factors, which are far from the area they affect, tend to locate in the genome in areas that Prof. Barkai and the members of the research group she heads previously identified as particularly open to evolutionary change.
But there are a large number of "trans" factors in the genome - from the transcription factors that bind directly to the genes to the receptors that receive information that reaches the cell from the environment. Which of them has changed? Later in the study, the scientists were surprised to discover that the most common changes were in the factors involved in sensing the environment and transferring this information to the genes. In other words, evolution's response to changing conditions was the direction of the cell's communication mechanisms with its environment. Once again the media has been proven guilty.
The scientists noticed that the hybrid yeasts matched Darwin's description of organisms that benefit from being hybrids (they grew faster than their parents), and offered explanations for the phenomenon. One possible explanation is based on the fact that "cis" and "trans" factors sometimes complement each other (a weak "cis" factor in one gene may accompany a strong "trans" factor, and vice versa). In some cases, a combination of strong "cis" and "trans" in the second allele may cause overexpression in the gene. In such a situation, the scientists expected to find one allele with a particularly high level of expression. This, indeed, was the case in 20% of cases. In the other cases, the two alleles had similar expression levels, but still beyond the range of the parents.
To their surprise, when they identified the genes that operate at an increased level of expression as a result of hybridization between the two species of yeast, the scientists discovered that these are mainly genes that play a role in respiration - the process in which the yeast uses sugar and sometimes oxygen to produce energy. The pure species rarely use oxygen. They kept the genes necessary for respiration, but reduced their expression using "trans" factors. Apparently, the combination between the two species caused these genes to "come out of the underground" and increase the activity level of the respiratory mechanism. It is possible that this activity contributed to the acceleration of growth.
The mechanisms for new genetic expression patterns in hybrids may explain various differences between the hybrids and their parents. Most hybrids are infertile and unable to reproduce (for example a mule, which is a hybrid of a donkey and a horse). But, there are species that are able to reproduce by other methods, and genome hybridization may be a convenient way to obtain new genetic traits quickly. Prof. Levy: "Hasmer serves us as a wonderful example that helps us understand how genomes that are far from each other work in complex organisms. Now we are preparing to apply what we learned from the yeast in bread wheat - a species that contains different genomes united in one nucleus."
20 תגובות
Chest:
You broke your promise again.
Although based on what you said before, I already knew there was no reason to believe you, but I thought you would keep at least a modicum of self-respect.
Michael,
I responded to my father as the site administrator.
This is a deliberate deception of the followers of Darwin.
It's even considered "scam"… think of it that way.
I know you are comfortable that I will not respond,
And I won't respond, because it won't help,
You are fixed and will remain so...
Chest:
Why do you break your promise?!
Hezi, the innovation in mutation is its very existence. not beyond Hence it cannot be assumed (logically or not) that the innovation will survive. On the contrary, most of the mutations do not survive further. Hence the assumption and conclusion of Chazi are flawed and fall short.
Evolution is not random. The genetic variation on which natural selection acts is random but natural selection is not random. The survival and success in producing offspring (fitness) of an individual is directly related to the ways in which the traits it has inherited function in the context of the environment. That is, an individual survives or produces offspring depending on its genes that express traits appropriate to the environment.
Evolution is a fact. Natural selection is the theory that explains the fact and has managed for over 150 years to not be far-fetched.
Avi,
You are also misleading the readers:
There is no debate that there was and is evolution.
The important question is whether evolution is "random"...
The "scientists" (probably those who work at the Discovery Institute) fail to prove, but also fail to disprove. The real scientists (without quotation marks) confirm evolution in dozens of cases every day.
Chest:
It turns out that even completely illogical thinking can sometimes yield a correct conclusion.
We congratulate you and thank you for your decision to stop littering.
To Michael and other followers of Darwin,
It has been more than 150 years that the best "scientists"
Trying to prove the theory and not succeeding,
It's a fact.
I will not continue to comment on this topic.
Because people here are "fixed".
wont help …
Chest:
Just because you repeat a certain nonsensical claim over and over does not make it true.
Random mutations happen unintentionally all the time.
Bacteria "learn" (and no one will return to the stupid debate about whether it is indeed learning) to overcome antibiotics and insects "learn" to overcome pesticides, literally every day and before our eyes.
Many examples of evolution were given here on the site and in the following link
http://www.talkorigins.org/pdf/faq-speciation.pdf
You will find examples of evolution that created new species.
I know I'm just talking to the wall and that there's no way you'll let the facts undermine your blind faith in the imaginary being who in your eyes manages to be good and benevolent even though he created the holocaust.
A.- Mating between two species does not create new situations from a genetic point of view, but rather the possibility of genes being expressed or not expressed. Only mutation (and not "mutation") creates new situations genetically.
(All the rest without letters...) The logic you described relied on a wrong assumption (see XNUMX) and therefore the sentence following the words "the logic says" is devoid of any logic and there are no innovations in hybridization of the type in question.
And hence the defect of evolution cannot welcome (nor does it have desires, intentions, nor manners) any innovation or "innovation", because there are none in such a hybrid.
And hence, of course, your conclusion has no basis.
And as for your face - you are the one who is not ready to understand: as for you, only agreeing with you that there is a God - call him by any name you want - he will want you. Well, there is no need for this, God, and everything that is set before us in the world proves these things!
I'm sorry that here they don't want to understand (not that they can't).
A- Mating between two species creates new situations genetically,
Which surpass in strength the ability of "innovations" in mutations.
Obviously, this is not what is defined as a "mutation".
logic says,
If evolution did occur due to random mutations (emphasis on randomness),
After all, a lot of "innovations" are created in such a pairing.
so,
The "Evolution" was supposed to receive innovations which welcome,
and not reject them.
Conclusion: Evolution is not random, but directed by a reason that makes sure that life is not created that is not planned in advance.
Hezi,
Mating between two species is not the creation of a mutation nor the creation of a "mutation" but simply a pairing. Mutations are created randomly by themselves (as a result of an error in replication) or as a result of radioactive damage that causes the error as above. The vast majority of these errors are harmful and prevent the development of a functional creature (offspring). The few cases that are not harmful, either do not cause any change at all or are inherent in them A beneficial change that can be manifested immediately (and will be manifested in the production of more offspring carrying the beneficial mutation) or that will be manifested when the external conditions give the creature carrying the mutation an advantage resulting from it.
Nothing of everything written here requires the intervention of an external intelligence (which therefore has no proof of its existence - on the contrary, many things prove its non-existence).
By the way, the mule has no advantage over the two species that make it up, it simply fits into some niche of human use that the horse and the donkey do not fill (and in South America the llama fills it).
To Michael:
The point I keep repeating:
Is the development of evolution random mutations or directed by intelligence.
The fact that in mating between species, new "mutations" are created, which are even more successful than both species together (separate),
But there is no further permission,
only proves that without intelligent initial planning of the inheritance,
There is no transmission of mutations that…
It's a shame to try to turn the matter around...
fresh,
An example of trans factors are transcription factors. These factors are proteins that bind to the sites that exist near genes (for example to promoters that are cis factors) and thus lead to the expression of genes.
The genes that code for transcription factors can be anywhere in the genome, including on different chromosomes than the ones where the genes they activate are located
Chest:
Of course there is no need to remind anyone of the fact (which you probably also know but try to hide) that it is possible to create mutations that are passed on to offspring and this is often done.
Chest:
Do you really not understand what a contradiction is?
Does the possibility of causing thousands of avalanches through an explosion also contradict the theory that avalanches form by themselves?
Without getting into technical terms from genetics,
Simple logic says that precisely this phenomenon contradicts the theory
Because new species are created from random mutations.
mating between two species,
It is the best means of creating "random mutations" on purpose.
And yet, there is no possibility of instilling this randomness into the next generation,
Because they weren't programmed for it in advance...
The way in which cis acts on elements that are adjacent to it in space is conceivable, but how can a trans factor affect an element that is distant from it? In what way does the trans do this?
Cis and trans are concepts that describe the active nature of a gene
When, in a simple way, elements that act in trans act on elements that are far from them, genes on other chromosomes or at a great distance (or extranuclear activity when used in certain contexts)
And elements that act in cis are elements that act on genetic components adjacent to them in space, promoters, operators and the like.
Cis and trans are not epigenetic factors, they are a definitional characterization of the mode of operation of a DNA segment or its product.
several questions
With the current technology, is it possible to map epigenetic factors such as cis and trans in the same way as genes can be mapped?
That is, is it possible to know that the organism has exactly X transs? Cis-is can still be relatively easy, but how can you tell how many trans-is there are in an organism? After all, there can be trans's that we are not aware of their existence, and then it will be difficult to know what caused a certain phenotype, because the cause of this phenotype can be either a normal gene or a cis or a trans.