We explain what genes are, how they work, how their structure is and how they are classified. Manipulation and genetic mutations.
What are the genes?
In biology , the minimum unit of genetic information that contains the DNA of a living being is known as genes . All genes together form the genome, that is, the genetic information of the species.
Each gene is a molecular unit that encodes a specific functional product , such as a protein . At the same time, it is responsible for transmitting said information to the offspring of the organism, that is , it is responsible for inheritance .
Genes are found within chromosomes (which in turn make life in the nucleus of our cells ). Each gene occupies a specific position, called the locus , along the gigantic sequential chain that composes the DNA .
Seen in another way, a gene is nothing more than a short segment of DNA, which is located within the chromosome always located in the same place, since they usually occur in paired pairs (known as alleles). That means that for each specific gene there is another allele , a copy.
The latter is very important in inheritance since some physical or physiological traits may be dominant (tend to manifest) or recessive (do not tend to manifest). The former are so powerful that a gene of the two alleles is enough to manifest, while the latter require that the two alleles be identical in order to manifest.
However, recessive genetic information can be inherited, since a person who does not manifest a specific gene can nevertheless transmit it to their offspring. This is what happens when someone with dark eyes has a light-eyed child, usually like one of their grandparents.
As will be seen, the information contained in the genes can determine many of our physical features , such as height, hair color, etc. But it can also cause congenital diseases or defects, such as trisomy 21 or Down syndrome.
History of the genes
The father of the concept of inheritance was the Austro-Hungarian naturalist and monk Gregor Johann Mendel (1822-1884), who determined in his studies that there was a set of specific traits inheritable from one generation to another.
Its appearance depended on what he called “factors” and what we know today as genes. Mendel assumed that these factors were arranged linearly in the chromosomes of the cells, which had not yet been studied in depth.
However, in 1950 the shape and structure of DNA was discovered , in its famous double helix . Thus the idea was imposed that these factors, now called “genes”, were nothing more than a fragment encoding the DNA sequence, the result of which was the synthesis of a specific polypeptide, that is, a fragment of a protein.
With this discovery the genetics are born and the first steps are taken towards the knowledge and manipulation of the genetic code .
How do genes work?
The genes operate as a template or a pattern (according to the genetic code), which determines the type of molecules and the place where they should go, in order to compose a macromolecule equipped with specific functions within the organism.
Seen this way, genes are part of the manufacturing mechanisms of life itself . It is a complex and self-regulated process, since various segments of the DNA itself operate as signals of beginning, end, increase or silencing of the transcription of gene content.
Types of genes
Genes differ according to their specific role in protein synthesis, as follows:
- Structural genes . Those that contain the coding information, that is, that which corresponds to the set of amino acids to form a specific protein.
- Regulatory genes . Genes that lack coding information, but instead fulfill regulatory and ordering functions, thus determining the place of beginning and end of genetic transcription, or fulfill specific roles during mitosis and meiosis , or denoting the place where they should Enzymes or other proteins are combined during synthesis.
Structure of a gene
Genes are, from a molecular point of view, little more than a sequence of the nucleotides that make up the DNA or RNA (adenine, guanine, cytosine and thymine or uracil). Its specific order corresponds to a specific set of amino acids, to form a macromolecule of specific function (proteins, for example).
However, genes are made up of two parts of different functions, which are:
- Exons . The region of the gene that contains the coding DNA, that is, the specific sequence of nitrogenous bases that allow to synthesize a protein.
- Introns . The region of the gene that contains non-coding DNA, that is, that does not contain instructions for protein synthesis.
A gene can have different numbers of exons and introns, and in some cases, such as in the DNA of prokaryotic organisms (structurally simpler than that of eukaryotes ), genes lack introns.
During the process of transcription of the genetic information of the DNA, and its recomposition in a new protein, or also during the stages of duplication and replication of the DNA in the cellular reproduction , it is possible, although not too common, that errors occur .
An amino acid replaces another within a protein, as a consequence, and depending on the type of substitution and the place in the macromolecule where the substitute amino acid is located, it may be a harmless error, or that it will trigger diseases, ailments or even benefits Unexpected These types of spontaneous errors are known as mutations .
The mutations occur spontaneously and play an important role in heredity and evolution . A mutation can give an species an ideal trait to better adapt to its environment, thus being favored by natural selection, or on the contrary it can provide an unfavorable trait and lead to extinction.
Only those positive traits spread throughout the species as the favored individual reproduces more than others, eventually giving rise to a new species.
The genome is the set of all the genes contained in the chromosomes, that is, the totality of the genetic information of a particular individual or species .
The genome is also the genotype , that is, the invisible and hereditary expression that largely produces physical and physiological features (the phenotype ). The origin of this term comes from the union of “gene” and “chromosome.”
In diploid cells (2n), that is, in which there are homologous pairs of chromosomes, the entire genome of the organism is found in two whole copies, while in haploid cells (n) only one copy is found.
The latter is the case of gametes or sex cells, which contribute half the genetic load of a new individual , completing it with that of the other gamete (male and female) to build a new genetically new individual.
Genetic engineering and gene therapy
As the functioning of genes has become more and more known, the genome of whole species has been decoded and technological tools are available to intervene in genetic information .
Currently, new biotechnological options have been born, such as genetic engineering (or genetic manipulation) and gene therapy, to name two famous cases.
Genetic engineering pursues the “programming” of living organisms by manipulating (adding, deleting, etc.) their genetic code. For this, nanotechnology or some genetically manipulated viruses are used .
Thus, it is possible to obtain animal or plant species with a desired phenotype, in a more extreme version of selective breeding (which we do with domestic animals ). Genetic engineering plays an important role in the food industry , in agriculture , livestock , etc.
On the other hand, gene therapy is a medical method of attack to incurable diseases such as cancer or inherited, such as Wiskott-Aldrich syndrome. It consists of the insertion of elements in the genome of an individual, directly in their cells or tissues.
For example, in the case of tumors, “suicidal” genes are introduced into the abnormal cells that lead to disintegration itself, causing the cancer to eliminate itself when it reproduces. This technique, however, is still in experimental and / or initial phases.