According to Abbreviationfinder, Deoxyribonucleic Acid is commonly known as DNA.
DNA composition
Support structure The support structure of a DNA strand is made up of alternating units of Phosphate and sugar groups. The sugar in DNA is a pentose, specifically, Deoxyribose.
- Phosphoric acid :
Its chemical formula is H 3 PO 4. Each nucleotide can contain one (monophosphate: AMP), two (diphosphate: ADP) or three (triphosphate: ATP) phosphoric acid groups, although as constituent monomers of nucleic acids they only appear in the form of monophosphate nucleosides.
- Deoxyribose :
Is a monosaccharide of 5 atoms of carbon (one Pentose) derived from ribose, part of the structure of the DNA nucleotide. Its formula is C 5 H 10O 4. One of the main differences between DNA and RNA is sugar, since in RNA the 2- Deoxyribose in DNA is replaced by an alternative Pentose, Ribose.
Sugar molecules are attached to each other through phosphate groups, which form phosphodiester bonds between the third (3 ′, “three prime”) and fifth (5 ′, “five prime”) carbon atoms of two adjacent sugar rings. Asymmetric bond formation implies that each DNA strand has a direction.
In a double helix, the direction of the nucleotides in one strand (3 ′ → 5 ′) is opposite to the direction in the other strand (5 ′ → 3 ′). This organization of the DNA strands is called antiparallel; they are parallel chains, but with opposite directions. In the same way, the asymmetric ends of DNA strands are called the 5 ′ end (“five prime”) and the 3 ′ end (“three prime”) respectively.
- Nitrogen bases :
The four major nitrogenous bases found in DNA are Adenine (abbreviated A), Cytosine (C), Guanine (G) and Thymine (T). Each of these four bases is attached to the sugar-phosphate backbone through the sugar to form the complete nucleotide (base-sugar-phosphate).
The bases are heterocyclic compounds and aromatic with two or more atoms of nitrogen, and, in the majority bases are classified into two groups: (adenine and guanine) purine or purine bases, derived from the Purine and formed by two rings linked each other, and pyrimidine or pyrimidine bases (cytosine and thymine), derived from Pyrimidine and with a single ring.
In nucleic acids there is a fifth pyrimidine base, called Uracil (U), which normally takes the place of thymine in RNA and differs from it in that it lacks a methyl group in its ring. Uracil is not usually found in DNA, it only appears rarely as a residual product of the degradation of cytosine by oxidative deamination processes.
- Thymine:
In the genetic code it is represented by the letter T. It is a pyrimidine derivative with an oxo group in positions 2 and 4, and a methyl group in position 5. It forms the Nucleoside Thymidine (always deoxythymidine since it only appears in DNA) and the Nucleotide Thymidylate or thymidine monophosphate (dTMP).
In DNA, thymine always pairs with adenine in the complementary strand through two hydrogen bonds, T = A. Its chemical formula is C 5 H 6 N 2 O 2 and its nomenclature 2, 4-dioxo, 5-methylpyrimidine.
- Cytosine:
In the genetic code it is represented by the letter C. It is a pyrimidine derivative, with an amino group in position 4 and an oxo group in position 2. It forms the Nucleoside Cytidine (deoxycytidine in DNA) and the Nucleotide Citidylate or (deoxy) cytidine monophosphate (dCMP in DNA, CMP in RNA).
Cytosine always pairs in DNA with the complementary strand guanine through a triple bond, C≡G. Its chemical formula is C 4 H 5 N 3 O and its nomenclature 2-oxo, 4 aminopyrimidine. Its molecular mass is 111.10 atomic mass units. Cytosine was discovered in 1894 when it was isolated from sheep thymus tissue.
- Adenine:
In the genetic code it is represented by the letter A. It is a derivative of purine with an amino group at position 6. It forms the nucleoside Adenosine (deoxyadenosine in DNA) and the nucleotide Adenylate or (deoxy) adenosine monophosphate (dAMP, AMP). DNA is always pairedwith thymine complementary strand through two hydrogen bonds, A = T. Its chemical formula is C 5 H 5 N 5 and its nomenclature is 6-aminopurine. Adenine, along with thymine, was discovered in 1885 by the German physician Albrecht Kossel.
- Guanine:
In the genetic code it is represented by the letter G. It is a puric derivative with an oxo group at position 6 and an amino group at position 2. It forms the nucleoside (deoxy) Guanosine and the nucleotide Guanylate or (deoxy) guanosine monophosphate (dGMP, GMP). Guanine always pairs in DNA with the complementary strand cytosine through three hydrogen bonds, G≡C. Its chemical formula is C 5 H 5 N 5 O and its nomenclature 6-oxo, 2-aminopurine.
There are also other nitrogenous bases (the so-called minority nitrogenous bases), derived naturally or synthetically from some other majority base. For example, Hypoxanthine, relatively abundant in TRNA, or Caffeine, both derived from adenine; others, such as Acyclovir, derived from guanine, are synthetic analogues used in antiviral therapy; others, such as one of the derivatives of uracil, are antitumor.
Nitrogen bases have a series of characteristics that give them certain properties. An important characteristic is its aromatic character, a consequence of the presence in the ring of double bonds in conjugated position. This gives them the ability to absorb light in the ultraviolet zone of the spectrum around 260 Nm, which can be used to determine the extinction coefficient of DNA and find the existing concentration of nucleic acids.
Another of their characteristics is that they present Tautomerism or Isomerism of functional groups due to the fact that a Hydrogen atom attached to another atom can migrate to a neighboring position; in nitrogenous bases there are two types of tautomeries: lactam-lactime tautomerism, where hydrogen migrates from nitrogen to oxygen of the oxo group (lactam form) and vice versa (lactime form), and imine-primary amine tautomerism, where hydrogen can be forming the amine group (primary amine form) or migrate to the adjacent nitrogen (imine form). Adenine can only have amine-imine tautomerism, thymine and uracil show double lactam-lacthyme tautomerism, and guanine and cytosine can have both. On the other hand, and although they are apolar molecules, the nitrogenous bases present enough polar character to establish hydrogen bridges, since they have very electronegative atoms (nitrogen and oxygen) presenting a negative partial charge, and hydrogen atoms with a positive partial charge., so that dipoles are formed that allow these weak links.
The human Haploid Genome is estimated to be around 3 billion base pairs. To indicate the size of DNA molecules, the number of base pairs is indicated, and as derivatives there are two widely used units of measurement, the Kilobase (kb), which is equivalent to 1,000 base pairs, and the Megabase (Mb), which is equivalent to one million base pairs.
