What are genes made of, What is a gene? History, Types of gene
What is a genes?
In biology, genes are known as the smallest unit of genetic information that the DNA of a living being contains. All genes together make up 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 such 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 a locus, along the gigantic sequence chain that makes up DNA.
Seen in another way, a gene is nothing more than a short segment of DNA, which is found 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 heredity since some of the physical or physiological traits can be dominant (they tend to manifest) or recessive (they do not tend to manifest). The former is so powerful that one gene from the two alleles is enough to manifest, while the latter requires that the two alleles be identical to manifest.
However, recessive genetic information can be inherited, since a person who does not manifest a specific gene can nevertheless pass it on to their offspring. This is what happens when someone with dark eyes has a child with light eyes, usually like one of his grandparents.
As will be seen, the information contained in genes can determine many of our physical traits, such as height, hair color, etc. But it can also cause congenital diseases or defects, such as trisomy 21 or Down syndrome.
It can help you: Chromosomal theory of inheritance
What are genes made of?
Genes are made of -The basic physical and functional unit of inheritance is genes. Genes are made up of DNA. Some genes serve as guidelines for making molecules called proteins. In humans, the gene varies from a few hundred DNA bases to over 2 million bases. International research called the Human Genome Project determined the sequence of the human genome and identified the gene that estimated humans to be 20,000-25,000.
History of genes
Mendel deduced the existence of genes from his experiments with plants.
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.
Their appearance depended on what he called “factors” and what we know today as genes. Mendel assumed that these factors were arranged linearly on the chromosomes of cells, which had not yet been studied in depth.
However, in 1950 the shape and structure of DNA were discovered, in its famous double helix. Thus the idea was imposed that these factors, now called “genes”, were nothing more than a coding fragment of the DNA sequence, the result of which was the synthesis of a specific polypeptide, that is, of a fragment of a protein.
With this discovery, genetics was born and the first steps were taken towards the knowledge and manipulation of the genetic code.
How do genes work?
Genes operate as a template or a pattern (according to the genetic code), which determines the type of molecules and the place where they must go, to compose a macromolecule endowed 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 for the beginning, end, increase or silencing of the transcription of the content of genes.
Different 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 that 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 that denotes the place where they should enzymes or other proteins combine during synthesis.
Structure of a gene
Genes are, from a molecular point of view, little more than a sequence of nucleotides that make up DNA or RNA (adenine, guanine, cytosine, and thymine or uracil). Their specific order corresponds to a specific set of amino acids, thus forming a macromolecule with a specific function (proteins, for example).
However, genes are made up of two parts with 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 a protein to be synthesized.
- Introns. The region of the gene that contains non-coding DNA, that is, it does not contain instructions for protein synthesis.
A gene can have different numbers of exons and introns, and in some cases, as in the DNA of prokaryotic organisms (structurally simpler than that of eukaryotes ), the genes lack introns.
The white lion is the result of a genetic mutation of the African lion.
During the process of transcription of genetic information from DNA, and its recomposition into a new protein, or also during the duplication and replication stages of DNA in cell reproduction, it is possible, although not very common, that errors occur.
One 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 mistake, or that it triggers 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 a species an ideal trait to better adapt to its environment, thus being favored by natural selection, or on the contrary, it can give it an unfavorable trait and lead it 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 given individual or species.
The genome is also the genotype, that is, the invisible and hereditary expression that largely produces the physical and physiological traits (the phenotype ). The origin of this term comes from the union of “gene” and “chromosome”.
In diploid (2n) cells, that is, in which there are pairs of homologous chromosomes, the entire genome of the organism is found in two whole copies, while in haploid (n) cells only one copy is found.
The latter is the case of gametes or sex cells, which provide half of 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
Genetic manipulation is used in medicine and the agricultural industry.
As the functioning of genes has become more and more known, the genome of entire 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 through the manipulation (addition, deletion, etc.) of their genetic code. This is used for nanotechnology or genetically engineered.
Thus, it is possible to obtain animal or plant species with the 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, agriculture, livestock, etc.
For its part, gene therapy is a medical method to attack incurable diseases such as cancer or hereditary, 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, “suicide” genes are introduced into abnormal cells that lead them to disintegrate themselves, causing cancer to kill itself as it reproduces. This technique, however, is still in experimental and/or early stages.
What are genes made of, What is a gene? History, Types of gene