Nucleobases (or Nucleotide bases) are the parts of RNA and DNA that may be involved in pairing (see also base pairs). Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known In Molecular biology, two Nucleotides on opposite complementary DNA or RNA strands that are connected via Hydrogen bonds are called These include cytosine, guanine, adenine, thymine (DNA) and uracil (RNA). Cytosine is one of the five main bases found in DNA and RNA. It is a Pyrimidine derivative with a Heterocyclic Aromatic ring Guanine is one of the five main Nucleobases found in the Nucleic acids DNA and RNA, the others being Adenine, Cytosine, Adenine is a Purine with a variety of roles in Biochemistry including Cellular respiration, in the form of both the energy-rich Adenosine Thymine is one of the four bases in the Nucleic acid of DNA that make up the letters ATGC Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Uracil is a common and naturally occurring Pyrimidine derivative Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units These are abbreviated as C, G, A, T, and U, respectively. They are usually simply called bases in genetics. Genetics (from Ancient Greek grc-Latn genetikos, “genitive” and that from grc-Latn genesis, “origin” a discipline of Biology, is Because A, G, C, and T appear in the DNA, these molecules are called DNA-bases; A, G, C, and U are called RNA-bases, respectively.

Uracil replaces thymine in RNA. These two bases are identical except that uracil lacks the 5' methyl group. Adenine and guanine belong to the double-ringed class of molecules called purines (abbreviated as R). Purine ( 1) is a heterocyclic Aromatic Organic compound, consisting of a Pyrimidine ring fused to an Imidazole ring Cytosine, thymine, and uracil are all pyrimidines (abbreviated as Y). Pyrimidine is a Heterocyclic Aromatic Organic compound similar to Benzene and Pyridine, containing two Nitrogen Atoms

The system of a base covalently bound to the 1' carbon of a ribose or deoxyribose is called a nucleoside, and a nucleoside with one or more phosphate groups attached at the 5' carbon is called a nucleotide. Carbon (kɑɹbən is a Chemical element with the symbol C and its Atomic number is 6 Ribose (ɹˈaɪbəʊs ɹˈaɪbəɹʊs primarily seen as D-ribose, is an Aldopentose — a Monosaccharide containing five Carbon Deoxyribose, also known as D-Deoxyribose and 2-deoxyribose, is an Aldopentose &mdash a Monosaccharide containing five Carbon See also Adenosine triphosphate (ATP A phosphate, an Inorganic chemical, is a salt of Phosphoric acid. Nucleotides are Organic compounds that consist of three joined structures a nitrogenous base a Sugar, and a Phosphate group

Apart from adenosine (A), cytidine (C), guanosine (G), thymidine (T) and uridine (U), DNA and RNA also contain bases that have been modified after the nucleic acid chain has been formed. In DNA, the only modified base is 5-methylcytidine (m5C). In RNA, there are many modified bases, including pseudouridine (Ψ), dihydrouridine (D), inosine (I), ribothymidine (rT) and 7-methylguanosine (m7G). ^[1][2]

Hypoxanthine and xanthine are two of the many bases created through mutagen presence, both of them through deamination (replacement of the amine-group with a hydroxyl-group). Hypoxanthine is a naturally occurring Purine derivative It is occasionally found as a constituent of Nucleic acids where it is present in the Anticodon Xanthine (ˈzænθiːn ˈzænθaɪn] (37-dihydro-purine-26-dione is a Purine base found in most body tissues and fluids and in other organisms In Biology, a mutagen ( Latin, literally origin of change) is a physical or chemical agent that changes the genetic information (usually DNA) Hypoxanthine is produced from adenine, xanthine from guanine. Adenine is a Purine with a variety of roles in Biochemistry including Cellular respiration, in the form of both the energy-rich Adenosine Guanine is one of the five main Nucleobases found in the Nucleic acids DNA and RNA, the others being Adenine, Cytosine, ^[3] Similarly, deamination of cytosine results in uracil. Cytosine is one of the five main bases found in DNA and RNA. It is a Pyrimidine derivative with a Heterocyclic Aromatic ring Uracil is a common and naturally occurring Pyrimidine derivative

Contents 1 Structure 1.1 Main bases 1.2 Modified purine bases 1.3 Modified pyrimidine bases 2 Novel Bases 3 References 4 See also 5 External links

Structure

• The "skeleton" of adenine and guanin is purine, hence the name purine-bases. Purine ( 1) is a heterocyclic Aromatic Organic compound, consisting of a Pyrimidine ring fused to an Imidazole ring
• The "skeleton" of cytosine, uracil and thymine is pyrimidine, hence pyrimidine-bases. Pyrimidine is a Heterocyclic Aromatic Organic compound similar to Benzene and Pyridine, containing two Nitrogen Atoms

Main bases

These are incorporated into the growing chain during RNA and/or DNA synthesis.

Nucleobase	Adenine	Guanine	Thymine	Cytosine	Uracil
Nucleoside	Adenosine A	Guanosine G	Thymidine T	Cytidine C	Uridine U

Modified purine bases

These are examples of modified adenosine or guanosine. Adenine is a Purine with a variety of roles in Biochemistry including Cellular respiration, in the form of both the energy-rich Adenosine Guanine is one of the five main Nucleobases found in the Nucleic acids DNA and RNA, the others being Adenine, Cytosine, Thymine is one of the four bases in the Nucleic acid of DNA that make up the letters ATGC Cytosine is one of the five main bases found in DNA and RNA. It is a Pyrimidine derivative with a Heterocyclic Aromatic ring Uracil is a common and naturally occurring Pyrimidine derivative Adenosine is a Nucleoside composed of a Molecule of Adenine attached to a Ribose sugar molecule ( Ribofuranose) moiety via a β-N9- Guanosine is a Nucleoside comprising Guanine attached to a Ribose ( Ribofuranose) ring via a β-N9- Glycosidic bond. Thymidine (more precisely called deoxythymidine; can also be labelled deoxyribosylthymine, and thymine deoxyriboside) is a Chemical compound Cytidine is a Nucleoside Molecule that is formed when Cytosine is attached to a Ribose ring (also known as a Ribofuranose) via Uridine is a molecule (known as a Nucleoside) that is formed when Uracil is attached to a Ribose ring (also known as a Ribofuranose) via a β-N1-

Nucleobase	Hypoxanthine	Xanthine	7-Methylguanine
Nucleoside	Inosine I	Xanthinosine X	7-Methylguanosine m7G

Modified pyrimidine bases

These are examples of modified cytidine, thymidine or uridine. Hypoxanthine is a naturally occurring Purine derivative It is occasionally found as a constituent of Nucleic acids where it is present in the Anticodon Xanthine (ˈzænθiːn ˈzænθaɪn] (37-dihydro-purine-26-dione is a Purine base found in most body tissues and fluids and in other organisms Inosine is a Nucleoside that is formed when Hypoxanthine is attached to a Ribose ring (also known as a Ribofuranose) via a β-N9-

Nucleobase	Uracil	5,6-Dihydrouracil	5-Methylcytosine
Nucleoside	Pseudouridine Ψ	Dihydrouridine D	5-Methylcytidine m5C

Novel Bases

Main article: Nucleic acid analogues

A vast number of nucleobases analogues exist. Uracil is a common and naturally occurring Pyrimidine derivative 5-Methylcytosine is a methylated form of Cytosine in which a Methyl group is attached to carbon 5 altering its structure without altering its base-pairing Pseudouridine (abbreviated Ψ is the C-glycoside Isomer of the Nucleoside Uridine, and it is the most prevalent of the over one hundred different modified Dihydrouridine (D is a Pyrimidine which is the result of adding two Hydrogen atoms to a Uridine, making it a fully saturated pyrimidine ring with Nucleic acid analogues are compounds structurally similar ( analog) to naturally occurring RNA and DNA used in medicine and in molecular biology research The most common application are used as fluorescent probes, either directly or indirectly, such as Aminoallyl nucleotide which are used to label cRNA or cDNA in microarrays. Aminoallyl nucleotides are used in post-labeling of nucleic acids to be used in Microarrays These nucleotides are formally known as 5-(3-amino Allyl For terminology see glossary below A DNA microarray is a High-throughput technology used in Molecular biology and in Several groups are working on alternative "extra" base pairs to extend the genetic code, such as isoguanine and isocytosine or the fluorescent 2-amino-6-(2-thienyl)purine and pyrrole-2-carbaldehyde. Isoguanine or 2-hydroxyladenine is a Purine base that is an Isomer of Guanine. Isocytosine or 2-aminouracil is a Pyrimidine base that is an Isomer of Cytosine.

In medicine, several nucleoside analogues are used as anticancer and antiviral agents. Nucleoside analogues are a range of antiviral products used to prevent Viral replication in infected cells The viral polymerase incorporates these compounds with non-canon bases. These compounds are activated in the cells by being converted into nucleotides, they are adminisered as nuclosides as charged nucleotides cannot easily cross cell membranes.

References

See also

• Nucleoside
• Nucleotide
• DNA
• RNA

External links

• Base pairing in DNA Double Helix (shows specific hydrogen bonds)

See also Adenosine triphosphate (ATP Nucleotides are Organic compounds that consist of three joined structures a nitrogenous base a Sugar, and a Phosphate group Deoxyribonucleic acid ( DNA) is a Nucleic acid that contains the genetic instructions used in the development and functioning of all known Ribonucleic acid ( RNA) is a Nucleic acid that consists of a long chain of Nucleotide units

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