DNA (Deoxyribonucleic acid)

Deoxyribonucleic acid, abbreviated as DNA, is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms and some viruses, and is responsible for its hereditary transmission. The main function of the DNA molecule is the long-term storage of information. Many times, DNA is compared to a plane or a recipe, or a code, as it contains the instructions needed to build other components of cells, such as proteins and RNA molecules. DNA segments carrying this genetic information are called genes, but the other DNA sequences have structural purposes or take part in regulating the use of this genetic information.
Situation of DNA within a eukaryotic cell.


Part of a double helix DNA structure
From the chemical point of view, DNA is a polymer of nucleotides, ie, a polynucleotide. A polymer is a compound formed by many simple units connected to each other, as if it were a long train formed by wagons. In DNA, each car is a nucleotide, and each nucleotide, in turn, consists of a sugar (the deoxyribose), a nitrogenous base (which may be adenine → A, thymine → T, cytosine → C or guanine → G ) And a phosphate group that acts as a coupling of each car with the next one. What distinguishes one car (nucleotide) from another is, then, the nitrogenous base, and hence the DNA sequence is specified by naming only the sequence of its bases. The sequential arrangement of these four bases along the chain (the ordering of the four types of wagons along the entire train) is the one encoding the genetic information: for example, a DNA sequence may be ATGCTAGATCGC .. In living organisms, DNA is presented as a double nucleotide chain, in which the two strands are linked together by connections called hydrogen bonds.

In order for the information contained in the DNA to be used by the cellular machinery, it must first be copied into nucleotide trains, shorter and with different units, called RNAs. RNA molecules are exactly copied from the DNA by a process called transcription. Once processed in the cell nucleus, the RNA molecules can emerge into the cytoplasm for later use. The information contained in the RNA is interpreted using the genetic code, which specifies the amino acid sequence of the proteins, according to a match of a nucleotide triplet (codon) for each amino acid. That is, genetic information (essentially: which proteins are to be produced at each point in the life cycle of a cell) is encoded in the DNA nucleotide sequences and must be translated in order to function. Such translation is done using the genetic code as a dictionary. The dictionary “nucleotide sequence-amino acid sequence” allows the assembly of long chains of amino acids (proteins) in the cytoplasm of the cell. For example, in the case of the above-indicated DNA sequence (ATGCTAGCATCG …), the RNA polymerase would use as a template the complementary strand of said DNA sequence (which would be TAC-GAT-CTA-GCG -…) for Transcribing a mRNA molecule to be read AUG-CUA-GAU-CGC -…; The resulting mRNA, using the genetic code, would be translated as the amino acid sequence methionine-leucine-aspartic acid-arginine -…

The DNA sequences that constitute the fundamental, physical and functional unit of heredity are called genes. Each gene contains a part that is transcribed into RNA and another that is responsible for defining when and where they should be expressed. The information contained in genes (genetics) is used to generate RNA and proteins, which are the basic components of cells, the “bricks” that are used for the construction of cellular organelles or organelles, among other functions.

Inside the cells, DNA is organized into structures called chromosomes that, during the cell cycle, are duplicated before the cell is divided. Eukaryotic organisms (eg, animals, plants and fungi) store most of their DNA within the cell nucleus and a small part in cellular elements called mitochondria, and in plastids and microtubule or centrile organizing centers, in case of have them; Prokaryotic organisms (bacteria and archaea) store it in the cytoplasm of the cell and, finally, the DNA viruses do it inside the capsid of a protein nature. There are many proteins, such as histones and transcription factors, which bind to DNA by providing it with a certain three-dimensional structure and regulating its expression. Transcription factors recognize DNA regulatory sequences and specify the pattern of transcription of genes. The complete genetic material of a chromosome endowment is called the genome and, with small variations, is characteristic of each species.