What is DNA? Its characteristics, parts and functions

DNA is probably the most well-known molecule of biological origin., this is found in all living beings on planet Earth. But... Why is DNA so important?

DNA (deoxyribonucleic acid) contains the necessary instructions for life: within our DNA is encoded the information necessary to make all the proteins in our body. Proteins fulfill many roles, determine the structure of cells and direct almost all metabolic processes in the body.

Differences in the genetic code are responsible for a multitude of phenomena that we observe in humans and animals: for example, why some people are more likely than others to develop certain diseases, or why dogs have tails, different eye colors or the group sanguine. All our physical and mental traits are determined by genetics, although the environment can then significantly influence our development.

We have all heard of DNA and we know its fundamental role in our body as the guardian of genetic information, but... Are there other functions? In this article we talk in depth about DNA, its structure and all its functions.

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What exactly is DNA?

DNA is the acronym for deoxyribonucleic acid. We can say that DNA is the building block of all living things, contains all genes necessary for the manufacture of proteins, essential molecules for the functioning of our body.

DNA contains our inherited material, which makes us who we are, no person has the same DNA as another: each person has a unique code contained in the long DNA molecule. The information contained in DNA is passed down from parent to child and approximately half of a child's DNA is of paternal origin and the other half is maternal.

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DNA structure

DNA is described as a polymer of nucleotides, that is, a long chain made up of small molecules.

Nucleotides are the fundamental units of deoxyribonucleic acid (DNA). Each nucleotide can be divided into three parts: a carbohydrate (2-deoxyribose), a nitrogenous base, and a phosphate group (derived from phosphoric acid).

Nucleotides are distinguished by their nitrogenous base, and it is the name of the base that is specified when presenting the DNA sequence, since the two other components are always the same. There are four different bases:

• Adenine (A)
• Cytosine (C)
• Guanine (G)
• Thymine (T)

DNA takes the form of a double helix, when viewed on a three-dimensional level; It is made up of two chains held together by hydrogen bonds., forming a double-stranded molecule. The base pairs form the ladder-like spiral, and the sugar phosphate backbone forms the supporting sides of the DNA helix.

The bases are aligned in sequential order along the chain, encoding the genetic information according to the criterion of complementarity: A-T and G-C. Adenine and guanine are larger in size than thymine and cytosine, making this complementarity criterion necessary for DNA to remain uniform.

Secondly, DNA is found in the cell nucleus of eukaryotes, as well as in chloroplasts and mitochondria. In prokaryotic organisms, the molecule is found free in the cytoplasm in an irregularly shaped body known as a nucleoid. Finally, it should be added that the structure of DNA differs between prokaryotic and eukaryotic cells. In eukaryotic cells it has a linear structure, and the ends of each chain are free; however, in prokaryotic cells the DNA is contained in a long, circular double strand.

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What is DNA for?

DNA has three main functions in the body: store information (genes and complete genome), produce proteins (transcription and translation) and duplicate to ensure that information is passed on to daughter cells during division cell phone.

The information needed to build and maintain an organism is stored in DNA, which is passed from parent to child. The DNA that carries this information is called genomic DNA, and the set of genetic information is called the genome. We have more than two meters of DNA, and our nuclei are much smaller: DNA is organized into compact molecules called chromatin, which correspond to the association of DNA, RNA and proteins. Chromatin then assembles into chromosomes, highly organized structures that allow cell divisions.

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The categories and parts of DNA

DNA can be divided into two broad categories: non-coding DNA and coding DNA. Let's see its specific functions.

1. The coding DNA

We cannot talk about coding DNA without talking about genes. A gene is a section of DNA that influences a trait or characteristic of an organism.such as eye color or blood type. Genes have coding regions called open reading frames, as well as sections of control called enhancers and promoters that influence the coding region to be transcribe. The total amount of information contained in the genome of an organism is called the genotype.

The DNA has the information for the manufacture of proteins, which are called the workers of the organism, and that fulfill a multitude of functions; some proteins are structural, like the proteins in hair or cartilage, while others are functional, like enzymes.

The body uses 20 different amino acids to make approximately 30,000 different proteins.. The DNA molecule has to tell the cell the order in which the amino acids should be joined.

Heredity determines which proteins will be produced, using DNA as a blueprint to build them. Sometimes changes in the DNA code (mutations) will cause proteins to not work properly, causing disease. At other times, however, code changes will cause beneficial alterations in individuals, who will then be better able to adapt to their environment.

A gene has DNA that is read and converted into a messenger RNA substance. This RNA transmits information between the gene's DNA and the machinery responsible for making proteins.. RNA acts as a blueprint for the production machinery so that amino acids are arranged and connected in the correct order to make a protein.

Although transcription to proteins is the basic role of DNA. The central dogma of biology DNA → RNA → protein has been shown to be wrong, and in fact there are multiple processes that influence and transfer information. Some viruses use RNA as the original material (RNA viruses), and the process of information flowing from RNA to DNA is known as reverse transcription or reverse transcription DNA. There are also non-coding RNA sequences that are created by transferring DNA sequences to RNA, and these can have a function without being made into proteins.

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2. non-coding DNA

About 90% of a person's genome does not code for proteins.. This part of the DNA is called non-coding DNA. DNA can be conceptually divided into two categories, protein-coding genes and non-genes. In many species, only a small portion of the DNA codes for proteins - the exons - and they only make up about 1.5% of the human genome.

Non-coding DNA, also known as junk DNA, is DNA that does not code for a protein: sequences such as introns, virus recombinations, etc. Until recently, this DNA was thought to be useless until recent studies showed that this is not the case. These sequences can regulate gene expression as they have an affinity for proteins that can bind to DNA and are called regulatory sequences.

Scientists have only identified a small percentage of all existing regulatory sequences. The reason for the presence of large amounts of non-coding DNA in eukaryotic genomes and Differences in genome size between different species remains an enigma in science. present. Although more and more functions of non-coding DNA are becoming known, such as:

2.1. the repetitive elements

Repetitive elements in a genome are also functional parts of a genome, make up more than half of all nucleotides. A group of scientists at Yale University recently found a non-coding DNA sequence which supposedly has a role in allowing humans to develop the ability to use tools.

2.2. Telomeres and Centromeres

Also, some DNA sequences are responsible for the structure of chromosomes. Telomeres and centromeres contain few or no coding genes, but are crucial for holding chromosome structure together.

23. DNA to RNA

Some genes do not code for proteins, but are transcribed into RNA molecules: ribosomal RNA, transfer RNA, and interfering RNA (RNAi).

2.4. alternative splice

The arrangement of introns and exons in some gene sequences is important because allows alternative splicing of pre-messenger RNA, creating different proteins from the same gene. Without this ability, the immune system would not exist.

2.5. Pseudogenes

Some non-coding DNA sequences come from genes that have been lost in the course of evolution. These pseudogenes can be useful because they can give rise to new genes with new functions.

2.6. small sections of DNA

Other non-coding DNA sequences come from the replication of small sections of DNA, which It is also useful because tracking these repetitive sections of DNA can help with studies of phylogeny.

conclusion

DNA is the molecule that contains hereditary information in humans; This information, contained in the DNA, allows the cell to know the order in which the amino acids that make up the proteins should be joined. Proteins are responsible for most of the body's functions and a problem in their manufacture can have great consequences on our health. However, when we talk about DNA → RNA → protein, we refer to the great dogma of biology and genes, forgetting 90% of DNA. Until recently, the role of DNA, which does not code for a protein, was considered useless, but studies Recently, more and more functions of these non-coding sequences called regulatory.