It is common to say
(a)
that there is a degree of similarity between the DNA in humans and chimpanzees up to 98%, while the most different people are not separated from each other only from half a%, this type of proximity is usually used in the similarity of genetic content as evidence On the health of evolutionary biology.
However, did no one turn to ask: Why does the degree of resemblance of humans with mouse reach 85% and with fruit flies reach 60%?
That this human erect bodied, huge in size, in all its intricacies and its many and extended details, resemble that of a fly so small?
Wasn't it more acceptable for the ratio to be 10% - or less than a maximum of - 20%?
In order to answer this important question, let's start with growth. Development. Evolutionary biologists have long convinced that the secret lies there. Despite our diversity, all of our embryos are humans, fish, and chickens ... are very similar
(b)
.
We know that during the development of an embryo from a fertilized egg zygote to a complete organism, genotype (those traits loaded on the sequence of genes in the DNA) begin to translate themselves into phenotype, those that you inherit from your father and mother, the color of the eyes, the shape of the hand, the hair Eye breadth ... etc, everything.
Developmental Biology research is interested in the study of Developmental Biology, that revolutionary stage of our growth. The amazing process that includes distinguishing this small sperm to a specific number of members with completely disparate details in a short period occupies an intrinsic value in biology, as the big question still arises: How does a gene know that we need To put an ear here, an eye there, and a toes on the other side?
Who gives him the command?
Developmental regulatory genes
To understand what this complex term means, let's start with a group of famous experiments carried out by Edward Lewis, a professor of "Caltech" for 30 years, who was awarded the Nobel in Medicine in 1995 for his work on fruit flies.
What Louis - a lover of fruit flies and flutes since his teens - discovered was actually something very strange.
He was able in one of
his experiments to isolate mutations in the
genes responsible for regulating the
construction plan of the
body fruit fly, instead of the
fly 's
body contains two wings, appeared to one of
four wings, which we have to
repeat the
whole cloves
1
of the
lobes body fly, he
discovered Lewis that it happened By modifying a set of developmental regulatory genes later called homeotic genes and known as HOX, what do those genes do?
Flies with four wings after adding a whole body lobe to them, and on the left is a natural fly.
(Social Media)
Ed Lewis' famous quad-winged fly on the cover of Science magazine.
When we talk about genes, it is usual to think that they are a specific sequence of the DNA units responsible for the formation of a protein for a specific characteristic in the body of the organism, such as the color of the eyes, hair, the shape of the nose, and the length of the neck, for example. As for the developmental regulatory genes
2,
they are not responsible for these traits, but You play the role of the general planner responsible for the growth of the fetus’s body until it becomes a complete being. It’s like having a movie of 250 scenes. Regulatory genes play the role of the director who says, “Put this scene here, and this is there, so be the car scene per minute. The 50 ", those genes activate or inhibit the more specialized genes at lower levels in specific places and specific dates, such as telling the nasal formation gene about the location and time to start creating a nose in the fetus, with a specific number, for example, one nose."
The function of regulatory genes is to give orders for making major body lobes.
(Social Media)
HOX genes are a type of developmental regulatory gene that controls the map of the fetus’s body along its axis from front to back, and from head to tail.
After the formation of the primary embryonic lobes, these genes determine the type of lobe structures, for example: feet, antennae, and wings in fruit flies, and in humans, different types of vertebrae, and in fish, a head with gills and a body with fins and a tail.
Sculpture genes, then, determine the identity of the lobes, but they do not themselves form those lobes.
In the following illustration, a comparison between some types of organisms in terms of the HOX genes, there are the same genes in different types, but they are only responsible for controlling the map of the axis of the body, it says: "Put a head here and a tail there", so the command is executed in the fish in a way and in the mouse In another way, but it's the same thing from the same gene.
A comparison of some species of HOX genes.
(Social Media)
After fully understanding those mutations and isolating the responsible regulatory gene, it became possible for us to use chemical signals to restore them again.
One of the most famous experiments at that point was obtaining fruit flies with feet in the location of their antennae, which was called Antennapedia, and we called this type of transformations: Homeotic transformations, we find those transformations in the birth defects in humans, the most famous of these defects is polydactyly It is the appearance of more than five toes on the hand or feet of humans, dogs and cats, via mutations in the regulatory gene set HOXd.
Right, a natural antennae fruit fly.
To the left, an antennae-footed fruit fly.
To understand more, let's go back to experiments. In 1995, a Swiss team led by Walter Gehring at the University of Basel succeeded in identifying the regulatory gene responsible for the appearance of eye
3
, the gene that says: “Put one eye here, and another there.” The team succeeded not only in getting fruit flies with eyes In the position of their feet - after activating this gene in a position where the position of the feet was supposed to be inhibited - they even transferred the regulatory gene responsible for displaying the eye from the mouse to the fruit fly, then activated it in the fruit fly and awaited the results, did the new fruit fly come out With the eyes of a mouse?
No.
It came out with the eyes of fruit flies, this explains to us the main and surprising idea of developmental regulatory genes, as it does not order the making of a mouse eye, and it is not exclusive to mice mainly, as it has nothing to do with the design of the eye, but its only function is a more general matter in making an eye only, and then making more genes An eye specialist that knows how to make it, the fruit fly eye.
The genes are not divided here to command and implement only, but are graded into levels of genes as the complexity of the organism increases, such as ordering a regulatory gene to design an eye there, then at a lower level another regulatory gene designs a human eye, then a final gene adds the blue color with the rest of the traits ... etc. .
A model for simplicity, expressing the pattern of decision making between levels of regulatory genes in the same organism.
(Social Media)
Most of the organisms now on Earth, such as humans, flies, mice, fish, etc., have inherited the same type of identical genes from their ancestors.
These organisms, despite their apparent differences, preserved several major genetic tools of general form or plan over a time span of 600 million years.
From that point of view, all the diversity in the biological content on this planet appears as a repetition of the same type of command with the same type of unit, but in multiple forms, now let's get a dinosaur from a chicken!
From teeth to beaks
One of the problems that biologists faced was understanding the transformation of the sharp teeth of dinosaurs into beaks in their descendants of birds, so this transformation process requires an enormous number of mutations over a period of time that is very short for the time it needs, but one of the most powerful solutions to that problem appeared in 2006 when Matthew observed Harris, a biologist at a laboratories at the University of Wisconsin, with his supervisor John Fallon, said that the beak of
4,
one of the chicken embryos he was working on, was no longer present. Then, through a careful observation, he discovered what happened, as the hen showed small conical cutting teeth at the beak, teeth of crocodiles.
An attempt to show teeth in chicken embryos prior to that experiment, as many researchers tried to transfer the regulatory genes responsible for showing teeth from the mouse to the hen embryo, and several experiments succeeded, but this was the first time that a chicken was able to evoke (activate) the same gene that was activated From before when its ancestors from the dinosaurs, scientists have been able to understand the mechanism of action of this mutation, and the experiment was repeated again to create a chicken with teeth. Other experiments succeeded with snakes that appeared with feet and blind cave fish born with eyes.
At that point, and recently it entered the
genetic editing techniques
5
CRISPR-Cas9 game in
order to
help us understand the
evolutionary adaptive mechanisms of
living organisms, where researchers have
succeeded in modifying the
feet of
chicken embryos, and limbs, and their faces, through CRISPR techniques-Cas9 to become more like Boslavha of dinosaurs The ones that were around 150 million years ago, by working to understand the mutation of regulatory genes responsible for the formation of these organisms' bodies.
Yes, we brought the dinosaur back, not by cloning it in the lab, but by returning the chicken to its parentage, to the dinosaur that evolved from it, wow!
Here appears the important role played by Evolutionary Development, known in popular science circles with the nickname EVO-DEVO, as it helps us to better understand the molecular events responsible for many of the amazing transformations in the fossil record, such as the emergence of whole lobes in the body of insects or the transformation of globin into myoglobin And hemoglobin through the process of duplication of duplication, or explaining the reasons for the rapid development of certain parts of the body compared to the rest of the allometry parts, such as the state of growth of the limbs of a bat. Developmental development through comparative research of regulatory genes gives us a better understanding of the evolutionary history itself and the biological restrictions imposed on its course.
An illustration of how an insect develops after doubling a lobe in its body.
(Social Media)
Long-footed mice like bats, fruit flies with larger body lobes, antennae-based legs and paws, crustaceans without claws, butterflies with different abilities to distinguish colors.
Yes, it is a kind of absurdity that raises attention and prompts us to seriously question the ethical nature of these experiments and their future, especially as we know that despite the amazing progress in gene editing techniques, we are still on the first path and what tools we have in our hands resemble the first Edison lamp.
Developmental development is a new science, we still have a lot to learn, and many mistakes to make. The most important questions about the origin of life and the universe itself still push us into further research, research that has always surprised us with results that confirm that the degrees of similarity between you and the fruit fly and the simple human mouse are closer. Much more than you might have thought, as you are duplicates of the same plan, carrying the same genetic essence that you inherited from your ancestors, this pushes us into an ocean of contemplation and the question: Who am I?
——————————————————————
(a) - Of course, comparative research between the genetic contents of different species remains difficult, meaning that there are several criteria that we can rely on to evaluate similarities or The differences between two species, these criteria include things like genome size, length, and number of genes or chromosomes.
(B) - It must be clarified here that these famous designs for the growth of embryos of a number of animals and humans are subject to controversy, as the first designed by Ernst Haykal falsified them, but here we are talking about the degree of similarity between the embryos we do not try to discuss the idea that the embryo summarizes its offspring
ontogeny recapitulates phylogeny