Recently, mathematics and computer science have contributed to the understanding of human development processes. They did not clarify specific details (what and when a particular cell does), but touched on fundamental developmental questions, such as: how can the simple become complex? How can development mechanisms that are unstable with respect to random errors ensure high fidelity of the final result?
Thanks to adaptive self-organization, non-living molecules can create a living cell, and cells with limited individual capabilities can form a multicellular organism capable of many things.
In trying to understand how an embryo builds itself, it is very useful to compare - and contrast - the development of this biological system with the usual ways of building objects.
All engineering projects have common features. First of all, any project has a plan - a drawing or some other diagram - clearly showing what we want to get in the end. The plan will not be part of this outcome; it will remain with the leaders.
Some results are easier to achieve not by describing using a drawing, but by using step-by-step instructions. This is the case in cooking or knitting.
But again, the impact on the object is made by the agent from outside, on the basis of his knowledge. External information is not present in projects under construction. Therefore, these objects of engineering art cannot be completed and self-replicated by themselves. And finally, most of the facilities are put into operation only after the completion of the work and the signing of the relevant papers confirming the completion of construction.
In biological engineering, there are no drawings or sketches of the final result. Structures are created, but nobody knows the end result. Structures are alive from the moment they appear and remain so during ontogenesis.
Of course, a fertilized egg contains information (in genes, in molecular structures, in the spatial distribution of concentrations of chemicals), but the relationship between this information and how the finished organism will ultimately look is far from unambiguous. This information predetermines, to some extent, the further sequence of events, but not the fact that the sequence will turn out to be just that. For example, with a gene mutation or a change in the concentration of a certain substance in a certain place, the sequence of events changes, and development follows an abnormal path.
The information contained in the embryo is read and processed by the embryo itself; he has no one to shift hard physical work or thinking about process optimization. This means that the responsibility for biological design rests with all its participants, and not with the leader, as in the case of engineering projects.
The process of creating a human body is controlled not by some separate parts of the embryo, but by the system as a whole. A living system must remain alive all the time, without shutdowns for repair or reconstruction. The systems of a multicellular organism have a certain autonomy, they are not controlled from a single center.
Proteins are the main building materials in biology. They create most of the physical structures that give shape to cells, they form channels and pumps that regulate the circulation of substances in cells. Proteins are used to build almost every organ in a multicellular organism.
In addition, proteins are catalysts. They trigger and control biochemical reactions and metabolic pathways that produce other components of the body, such as DNA, fats and carbohydrates.
Protein is made up of a long chain of individual blocks - amino acids. For the construction of proteins, twenty types of amino acids are used, differing in structure and chemical properties. They interact with each other, which means that chains of amino acids can twist into intricate shapes - spontaneously or under the influence of other proteins. This twisting process is so complex that it is impossible to predict just the amino acid sequence which protein will result.
Different proteins are made up of different amino acid sequences. The amino acid sequence is encoded in the gene. There is no other information in the gene. Amino acids, one by one, attach to the growing protein chain in an order that is established by a molecule called messenger RNA (abbreviated as mRNA).
Messenger RNA is a copy of DNA created in a process called transcription. On DNA are genes, DNA regions, limited by the reading frame. Each gene encodes one protein. Encodes i.e. indicates the sequence of amino acids in a protein built in a cell. The genes are read using the protein structures of the cell, as shown in the figure.
To read or not to read a given gene is determined by the protein structures of the cell (ribosome) and promoters (DNA regions) that receive information from signaling molecules around the cell. The specialization of cells is that cells, for example, of the liver, read only genome genes related to the construction of the liver.
A gene is an indivisible piece of genetic information that determines the sequence of amino acids in one protein, enclosed in a reading frame. At the beginning of a gene, short base sequences are located that help protein reading complexes find the beginning of a gene on DNA. At the end is a stop codon indicating the end of the reading.
In the processes of meiosis (formation of germ cells from somatic cells), the somatic cell is divided into two parts, while genetic information is randomly distributed between new cells. The double set of chromosomes diverges into the resulting germ cells. In this case, the chromosomes do not pass into the germ cells entirely, but exchange parts, but in such a way that the genes remain undivided. Hence the concept of "gene indivisibility" arises.
Each reproductive cell has not a double, but a single set of chromosomes. Due to the random nature of the meiosis process, the genetic composition of germ cells differs from the genetic makeup of each parent and is not the same in each cell. Which cell is the first to reach the female reproductive cell and penetrate into it, this is also determined by chance.
Thus, the genome of a fertilized cell (zygote) consists of a random sample from the genetic set of parents. The zygote already has a double set of chromosomes, formed by the fusion of two sex cells of the parents.
And the parents at one time had the same situation. This means that the child's genome contains genes from the genetic set of ancestors. In ontogeny, after transcription, rewriting information from DNA to messenger mRNA, the latter, through the nuclear membrane, enters the area of cell metabolism. After mRNA editing (splicing), the process of reading on the ribosome information from the mRNA and constructing (translation) in accordance with it from 20 amino acids of the corresponding protein begins, as indicated in the figure.
Since the properties of a protein also depend on its folding method, which is not indicated in the gene information, the properties of a protein are not completely determined by the gene information.
The connection between DNA bases (there are four of them, but it is their order in the gene that contains genetic information) and 20 amino acids is carried out using a universal genetic code, which is the same for all living things.
Each triplet (three bases in a row is one letter) of bases (there are only 4 bases, and there are 64 triplets) corresponds to a certain amino acid. Since only 20 triplets are required to establish a one-to-one correspondence between bases and amino acids, some triplets turn out to be duplicates, and therefore several different triplets can encrypt one amino acid. 64 is the number of possible combinations of 4 bases of 3, taking into account the sequence. The established correspondence of triplets and amino acids is called the genetic code.
The cells in the body are specialized and they synthesize only certain proteins that they need. Not all genes of the genome are read in a cell, but only those that are needed for the production of proteins of this particular cell at the moment.
This is achieved by the fact that the readout complexes contain the proteins of a given cell, which, based on bases at the beginning of the gene, recognize their gene and read information from it. Proteins determine the genes to be read, and these genes control the production of new proteins.
The cells of different organs of the body differ from each other and synthesize different types of proteins. For example, intestinal cells make proteins that allow you to digest food, ovarian cells synthesize proteins for sex hormones, and white blood cells make proteins to fight germs. All of these cells contain all the genes of the genome, even those they will never need. However, only the genes needed by specific cells at a given time are read.
When the situation changes, which is determined by signaling molecules outside the cell that respond to the environment, then other genes begin to be read to satisfy the emerging need. The process of reading genes is controlled by the cell itself and the environment. This is adaptive self-regulation.
Adaptive because the regulation process is not set once and for all, but is controlled by the environment.
It is important to consider this if we create some restrictions and rules for a biological system. Such restrictions are characteristic of selection processes in biology or for social societies in which laws and restrictive moral norms are created. The processes of cultural evolution change the social environment, therefore the established norms and rules, which seemed reasonable yesterday, may turn out to be obstacles to further development after a while. This will create tension in society, and if it is not detected and corrected in time, there will be a certain chaos and further development will not be completely controllable.
GENES, ENVIRONMENT, BEHAVIOR.
Many people believe that biological information begins in the genes and goes from them higher, outward. Nobody tells the gene what to do. Always the opposite. Genes give commands, biological systems obey. Genes dictate cell structure and function. And if these cells are neurons, their functions include thinking, feeling, and behavior. Continuing this logic, we reach the conclusion that genes make us do what we do. This is the point of view of a genetic determinist.
It is reasonably believed that the gene is the unit of selection. But this does not mean that when building a new organism, only relatively old information recorded in genes is taken into account; information from the external environment, information that is present here and now, is also taken into account. It turns out that proteins are adapted by the external environment, and their properties are only partially determined by genes.
A gene section of DNA with recorded information about the structure of the protein does not carry any behavior, not any thought or emotion. Its information will be rewritten (copied) in the process of transcription onto an mRNA molecule, which will penetrate through the nuclear membrane into the area of cell metabolism, and there, after editing (splicing), the corresponding protein molecule is constructed in accordance with this information. The building blocks of protein molecules are 20 amino acids, and the information from the genes determines which and in what order they must be sequentially linked to make the protein. There is no other information in the gene.
Each property of the body is determined by many proteins. Sometimes in this set, one protein critically affects a certain property. But a small change in the cascade of chemical reactions, or even in the time of their course, sequentially taking place in the body, will lead to a change in the situation and the effect of this protein may cease to be critical. Therefore, it is incorrect to present a gene as the only reason for the occurrence of a property. It can be imagined that genes influence properties through a mass of intermediaries that can block or, on the contrary, enhance this influence. There is no unambiguous connection between the gene and the properties of the organism.
In the body, proteins can be - hormones, neurotransmitters, signaling molecules, enzymes. Thus, enzyme proteins catalyze the course of biochemical reactions and play an important role in metabolism. Some proteins have a structural or mechanical function to form a cytoskeleton that maintains the shape of cells. Proteins also play a key role in the immune response and in the cell cycle.
Many proteins are essential for the brain to function. But all of them usually do not determine behavior, but only cause a tendency to react to the environment in a certain way. Genetic vulnerability, predisposition, addiction, but rarely genetic inevitability.
It is also important to understand that genes are not independent commanders. Genes have regulatory regions (promoters) on their DNA. What for? So that the environment around the cell, through signaling molecules, could influence the activity (transcription factors) of the gene.
In essence, promoters allow the introduction of environmentally controlled conditions. When and how genes work is decided for them by other factors that regulate their activity. These are often environmental factors.
In addition, one must understand that genes are chemical molecules and under the influence of the environment they can change (mutate). A gene mutation leads to the construction of another protein in the cell, a change in the cascade of sequential biological reactions, possibly a certain change in the result, an effect on some properties of the organism, which may be its behavior.
Often methyl groups adhere to DNA, which make it difficult to read information from some genes, which is equivalent to a change in their activity. This effect, called DNA methylation, is one of the transcription factors that affect not genes, but information transmitted by them to the field of protein construction. On the ribosome, according to this altered information, another protein will be synthesized, which will slightly change the entire cascade of subsequent biochemical reactions.
When thinking about genes or environment, it is easy to go to one of the extremes. Either - genetic determinism, if we assume that genes are invincible commanders, or into Lysenkoism, if we assume that the external environment decides everything. The truth is between these extremes.
Let's look from a more general point of view at the stated question. Suppose genes are independent commanders. Then they all do their job regardless of anything. This raises two questions. How in living nature is it possible for some organ to work independently of anything? This doesn't happen.
And the second question - how can a variety of cells in the body appear from one initial cell? Genes would have to just churn out copies, because they are replicators. In the human body, according to Wikipedia, there are about 230 types of cells of different organs.
It can be assumed that this is a task written in the promoters for all types of cells. Then the promoters will be like the State Planning Committee: just as cumbersome and just as ineffective. But this is not the case. They, too, are only a link for the transmission of information from signaling molecules.
Whose will do these molecules carry? Whose mind controls the process? Signaling molecules carry information about the state of their external environment, the environment in which they are located. These signals can induce cell differentiation (specialization). Here it is a channel affecting the results of the work of the entire set of genes (genome). Not all genes are involved in the construction of some organ tissue, not all genes are involved in the synthesis of the insulin or neurotransmitter required at the moment.
Reason is nowhere to be seen, this is a process of self-organization of matter, in which genes are some kind of transmission link of information from the past, and not commanders. This whole process is a real brain, more precisely, the brain is a virtual semblance of this process. When we wonder how such complex processes occur without the participation of the brain, they occur on real biological objects, where everything is serious.
All variants of phenotypes that do not undergo natural Darwinian selection are rejected and die irrevocably. If we solved an engineering problem with the help of reason, then inappropriate options would simply be eliminated without any bloodshed. But the mind cannot do such tasks.
As for people, we firmly know that upbringing and education have a significant impact on behavior and thinking.
On the one hand, neurons, brain, hormones and genes. On the other hand, education and all kinds of environmental influences, including social institutions.
It makes no sense to contrast these two sides. We need to talk about the interaction of these two factors.
The system of regulation of human behavior based on the structures of the brain and receptors (sensory organs) is based on an organism that is already equipped with a system of genetic regulation, so it is clear that it cannot be independent. In addition, it must be adaptive, change under the influence of the social environment.
The processes of cultural evolution change the social environment, therefore the established norms and rules, which seemed reasonable only yesterday, may turn out to be obstacles to further evolution after a while. This will create tension in society, and if it is not detected and corrected in time, there will be a certain chaos and further development will not be completely controllable.