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NUCLEIC ACIDS are biopolymers , or large biomolecules , essential to all known forms of life . They are composed of monomers , which are nucleotides made of three components: a 5-carbon sugar , a phosphate group, and a nitrogenous base . If the sugar is a simple ribose , the polymer is RNA
RNA
(ribonucleic acid); if the sugar is derived from ribose as deoxyribose , the polymer is DNA
DNA
(deoxyribonucleic acid).

Nucleic acids are the most important of all biomolecules. They are found in abundance in all living things, where they function to create and encode and then store information in the nucleus of every living cell of every life-form organism on Earth. In turn, they function to transmit and express that information inside and outside the cell nucleus—to the interior operations of the cell and ultimately to the next generation of each living organism. The encoded information is contained and conveyed via the nucleic acid sequence , which provides the 'ladder-step' ordering of nucleotides within the molecules of RNA and DNA.

Strings of nucleotides are bonded to form helical backbones—typically, one for RNA, two for DNA—and assembled into chains of base-pairs selected from the five primary, or canonical, nucleobases , which are: adenine, cytosine, guanine, thymine, and uracil; note, thymine occurs only in DNA
DNA
and uracil only in RNA. Using amino acids and the process known as protein synthesis , the specific sequencing in DNA
DNA
of these nucleobase-pairs enables storing and transmitting coded instructions as genes . In RNA, base-pair sequencing provides for manufacturing new proteins that determine the frames and parts and most chemical processes of all life forms.

CONTENTS

* 1 History of nucleic acids * 2 Occurrence and nomenclature * 3 Molecular composition and size * 4 Topology * 5 Nucleic acid
Nucleic acid
sequences

* 6 Types of nucleic acids

* 6.1 Deoxyribonucleic acid * 6.2 Ribonucleic acid * 6.3 Artificial nucleic acid

* 7 Further reading * 8 See also * 9 Notes and references * 10 Bibliography * 11 External links

HISTORY OF NUCLEIC ACIDS

* Nuclein were discovered by Friedrich Miescher
Friedrich Miescher
in 1869. * In 1889 Richard Altmann discovered that nuclein has acidic properties, and it became called nucleic acid * In 1938 Astbury and Bell published the first X-ray diffraction pattern of DNA. * In 1953 Watson and Crick determined the structure of DNA
DNA
.

Experimental studies of nucleic acids constitute a major part of modern biological and medical research , and form a foundation for genome and forensic science , and the biotechnology and pharmaceutical industries .

OCCURRENCE AND NOMENCLATURE

The term nucleic acid is the overall name for DNA
DNA
and RNA, members of a family of biopolymers , and is synonymous with polynucleotide . Nucleic acids were named for their initial discovery within the nucleus , and for the presence of phosphate groups (related to phosphoric acid). Although first discovered within the nucleus of eukaryotic cells, nucleic acids are now known to be found in all life forms including within bacteria , archaea , mitochondria , chloroplasts , viruses , and viroids . (note: there is debate as to whether viruses are living or non-living ). All living cells contain both DNA
DNA
and RNA
RNA
(except some cells such as mature red blood cells), while viruses contain either DNA
DNA
or RNA, but usually not both. The basic component of biological nucleic acids is the nucleotide , each of which contains a pentose sugar (ribose or deoxyribose ), a phosphate group, and a nucleobase . Nucleic acids are also generated within the laboratory, through the use of enzymes ( DNA
DNA
and RNA polymerases) and by solid-phase chemical synthesis . The chemical methods also enable the generation of altered nucleic acids that are not found in nature, for example peptide nucleic acids .

MOLECULAR COMPOSITION AND SIZE

Nucleic acids are generally very large molecules. Indeed, DNA molecules are probably the largest individual molecules known. Well-studied biological nucleic acid molecules range in size from 21 nucleotides (small interfering RNA
RNA
) to large chromosomes (human chromosome 1 is a single molecule that contains 247 million base pairs ).

In most cases, naturally occurring DNA
DNA
molecules are double-stranded and RNA
RNA
molecules are single-stranded. There are numerous exceptions, however—some viruses have genomes made of double-stranded RNA
RNA
and other viruses have single-stranded DNA
DNA
genomes, and, in some circumstances, nucleic acid structures with three or four strands can form.

Nucleic acids are linear polymers (chains) of nucleotides. Each nucleotide consists of three components: a purine or pyrimidine nucleobase (sometimes termed nitrogenous base or simply base), a pentose sugar , and a phosphate group. The substructure consisting of a nucleobase plus sugar is termed a nucleoside . Nucleic acid
Nucleic acid
types differ in the structure of the sugar in their nucleotides–DNA contains 2'-deoxyribose while RNA
RNA
contains ribose (where the only difference is the presence of a hydroxyl group ). Also, the nucleobases found in the two nucleic acid types are different: adenine , cytosine , and guanine are found in both RNA
RNA
and DNA, while thymine occurs in DNA
DNA
and uracil occurs in RNA.

The sugars and phosphates in nucleic acids are connected to each other in an alternating chain (sugar-phosphate backbone) through phosphodiester linkages. In conventional nomenclature , the carbons to which the phosphate groups attach are the 3'-end and the 5'-end carbons of the sugar. This gives nucleic acids directionality , and the ends of nucleic acid molecules are referred to as 5'-end and 3'-end. The nucleobases are joined to the sugars via an N-glycosidic linkage involving a nucleobase ring nitrogen (N-1 for pyrimidines and N-9 for purines) and the 1' carbon of the pentose sugar ring.

Non-standard nucleosides are also found in both RNA
RNA
and DNA
DNA
and usually arise from modification of the standard nucleosides within the DNA
DNA
molecule or the primary (initial) RNA
RNA
transcript. Transfer RNA (tRNA) molecules contain a particularly large number of modified nucleosides.

TOPOLOGY

Double-stranded nucleic acids are made up of complementary sequences, in which extensive Watson-Crick base pairing results in a highly repeated and quite uniform double-helical three-dimensional structure . In contrast, single-stranded RNA
RNA
and DNA
DNA
molecules are not constrained to a regular double helix, and can adopt highly complex three-dimensional structures that are based on short stretches of intramolecular base-paired sequences including both Watson-Crick and noncanonical base pairs, and a wide range of complex tertiary interactions.

Nucleic acid
Nucleic acid
molecules are usually unbranched, and may occur as linear and circular molecules. For example, bacterial chromosomes, plasmids , mitochondrial DNA
DNA
, and chloroplast DNA
DNA
are usually circular double-stranded DNA
DNA
molecules, while chromosomes of the eukaryotic nucleus are usually linear double-stranded DNA
DNA
molecules. Most RNA
RNA
molecules are linear, single-stranded molecules, but both circular and branched molecules can result from RNA
RNA
splicing reactions.

NUCLEIC ACID SEQUENCES

Main article: Nucleic acid sequence

One DNA
DNA
or RNA
RNA
molecule differs from another primarily in the sequence of nucleotides . Nucleotide sequences are of great importance in biology since they carry the ultimate instructions that encode all biological molecules, molecular assemblies, subcellular and cellular structures, organs, and organisms, and directly enable cognition, memory, and behavior (See: Genetics ). Enormous efforts have gone into the development of experimental methods to determine the nucleotide sequence of biological DNA
DNA
and RNA
RNA
molecules, and today hundreds of millions of nucleotides are sequenced daily at genome centers and smaller laboratories worldwide. In addition to maintaining the GenBank nucleic acid sequence database, the National Center for Biotechnology Information (NCBI, http://www.ncbi.nlm.nih.gov) provides analysis and retrieval resources for the data in GenBank and other biological data made available through the NCBI Web site

TYPES OF NUCLEIC ACIDS

DEOXYRIBONUCLEIC ACID

Main article: DNA
DNA

Deoxyribonucleic acid (DNA) is a nucleic acid containing the genetic instructions used in the development and functioning of all known living organisms. The DNA
DNA
segments carrying this genetic information are called genes. Likewise, other DNA
DNA
sequences have structural purposes, or are involved in regulating the use of this genetic information. Along with RNA
RNA
and proteins, DNA
DNA
is one of the three major macromolecules that are essential for all known forms of life. DNA
DNA
consists of two long polymers of simple units called nucleotides, with backbones made of sugars and phosphate groups joined by ester bonds. These two strands run in opposite directions to each other and are, therefore, anti-parallel. Attached to each sugar is one of four types of molecules called nucleobases (informally, bases). It is the sequence of these four nucleobases along the backbone that encodes information. This information is read using the genetic code, which specifies the sequence of the amino acids within proteins. The code is read by copying stretches of DNA
DNA
into the related nucleic acid RNA
RNA
in a process called transcription. Within cells DNA
DNA
is organized into long structures called chromosomes. During cell division these chromosomes are duplicated in the process of DNA
DNA
replication, providing each cell its own complete set of chromosomes. Eukaryotic organisms (animals, plants, fungi, and protists) store most of their DNA
DNA
inside the cell nucleus and some of their DNA
DNA
in organelles, such as mitochondria or chloroplasts. In contrast, prokaryotes (bacteria and archaea) store their DNA
DNA
only in the cytoplasm. Within the chromosomes, chromatin proteins such as histones compact and organize DNA. These compact structures guide the interactions between DNA
DNA
and other proteins, helping control which parts of the DNA
DNA
are transcribed.

RIBONUCLEIC ACID

Main article: RNA
RNA

Ribonucleic acid (RNA) functions in converting genetic information from genes into the amino acid sequences of proteins. The three universal types of RNA
RNA
include transfer RNA
RNA
(tRNA), messenger RNA (mRNA), and ribosomal RNA
RNA
(rRNA). Messenger RNA
RNA
acts to carry genetic sequence information between DNA
DNA
and ribosomes, directing protein synthesis. Ribosomal RNA
RNA
is a major component of the ribosome, and catalyzes peptide bond formation. Transfer RNA
RNA
serves as the carrier molecule for amino acids to be used in protein synthesis, and is responsible for decoding the mRNA. In addition, many other classes of RNA
RNA
are now known.

ARTIFICIAL NUCLEIC ACID

Main article: Nucleic acid analogue

Artificial nucleic acid analogues have been designed and synthesized by chemists, and include peptide nucleic acid , morpholino - and locked nucleic acid , glycol nucleic acid , and threose nucleic acid . Each of these is distinguished from naturally occurring DNA
DNA
or RNA
RNA
by changes to the backbone of the molecules.

FURTHER READING

Palou-Mir, Joana; Barceló-Oliver, Miquel; Sigel, Roland K.O. (2017). "Chapter 12. The Role of Lead(II) in Nucleic Acids". In Astrid, S.; Helmut, S.; Sigel, R. K. O. Lead: Its Effects on Environment and Health. Metal Ions in Life
Life
Sciences. 17. de Gruyter. pp. 403–434. doi :10.1515/9783110434330-012 .

SEE ALSO

* History of biochemistry * History of molecular biology * History of RNA
RNA
biology * Comparison of nucleic acid simulation software * Molecular biology * Nucleic acid structure * Nucleic acid methods * Nucleic acid thermodynamics * Oligonucleotide synthesis * Quantification of nucleic acids

NOTES AND REFERENCES

* ^ He called them nuclein. * ^ Bill Bryson
Bill Bryson
, A Short History of Nearly Everything , Broadway Books, 2005, p. 500. * ^ "What is DNA". What is DNA. Linda Clarks. Retrieved 6 August 2016. * ^ Dahm, R (January 2008). "Discovering DNA: Friedrich Miescher and the early years of nucleic acid research". Human Genetics. 122 (6): 565–81. ISSN 0340-6717 . PMID 17901982 . doi :10.1007/s00439-007-0433-0 . * ^ Cox, Michael; Nelson, David (2008). Principles of Biochemistry. Susan Winslow. p. 288. ISBN 9781464163074 . * ^ " DNA
DNA
Structure". What is DNA. Linda Clarks. Retrieved 6 August 2016. * ^ International Human Genome Sequencing Consortium (2001). "Initial sequencing and analysis of the human genome" (PDF). Nature. 409 (6822): 860–921. Bibcode :2001Natur.409..860L. PMID 11237011 . doi :10.1038/35057062 . * ^ Venter, JC; et al. (2001). "The sequence of the human genome." (PDF). Science. 291 (5507): 1304–1351. Bibcode :2001Sci...291.1304V. PMID 11181995 . doi :10.1126/science.1058040 . * ^ Budowle B, van Daal A (April 2009). "Extracting evidence from forensic DNA
DNA
analyses: future molecular biology directions". BioTechniques. 46 (5): 339–40, 342–50. PMID 19480629 . doi :10.2144/000113136 . * ^ A B Alberts, Bruce (2008). Molecular biology of the cell. New York: Garland Science. ISBN 0-8153-4105-9 . * ^ Elson D (1965). "Metabolism of nucleic acids (macromolecular DNA
DNA
and RNA)". Annu. Rev. Biochem. 34: 449–86. PMID 14321176 . doi :10.1146/annurev.bi.34.070165.002313 . * ^ National Institute of Health (September 28, 2007). "Discovering DNA: Friedrich Miescher
Friedrich Miescher
and the early years of nucleic acid research". Hum. Genet. nih.gov. 122 (6): 565–81. PMID 17901982 . doi :10.1007/s00439-007-0433-0 . * ^ Aparadh, V. T. ">(PDF). ISSN 2319-8877 . * ^ A B Brock, Thomas D.; Madigan, Michael T. (2009). Brock biology of microorganisms. Pearson / Benjamin Cummings. ISBN 0-321-53615-0 . * ^ Hardinger, Steven; University of California, Los Angeles (2011). "Knowing Nucleic Acids" (PDF). ucla.edu. * ^ Mullis, Kary B. The Polymerase Chain Reaction (Nobel Lecture). 1993. (retrieved December 1, 2010) http://nobelprize.org/nobel_prizes/chemistry/laureates/1993/mullis-lecture.html * ^ Verma S, Eckstein F (1998). "Modified oligonucleotides: synthesis and strategy for users". Annu. Rev. Biochem. 67: 99–134. PMID 9759484 . doi :10.1146/annurev.biochem.67.1.99 . * ^ A B Stryer, Lubert; Berg, Jeremy Mark; Tymoczko, John L. (2007). Biochemistry. San Francisco: W.H. Freeman. ISBN 0-7167-6766-X . * ^ Gregory SG, Barlow KF, McLay KE, et al. (May 2006). "The DNA sequence and biological annotation of human chromosome 1". Nature. 441 (7091): 315–21. Bibcode :2006Natur.441..315G. PMID 16710414 . doi :10.1038/nature04727 . * ^ Todorov TI, Morris MD (April 23, 2002). National Institutes of Health . "Comparison of RNA, single-stranded DNA
DNA
and double-stranded DNA
DNA
behavior during capillary electrophoresis in semidilute polymer solutions". Electrophoresis. nih.gov. 23 (7–8): 1033–44. PMID 11981850 . doi :10.1002/1522-2683(200204)23:7/83.0.CO;2-7 . * ^ Margaret Hunt; University of South Carolina (2010). "RN Virus Replication Strategies". sc.edu. * ^ McGlynn Peter; Robert G. Lloyd (June 10, 1999). "RecG helicase activity at three- and four-strand DNA
DNA
structures". oxfordjournals.org. ISSN 1362-4962 . * ^ Rich A, RajBhandary UL (1976). "Transfer RNA: molecular structure, sequence, and properties". Annu. Rev. Biochem. 45: 805–60. PMID 60910 . doi :10.1146/annurev.bi.45.070176.004105 . * ^ Watson JD, Crick FH (April 1953). "Molecular structure of nucleic acids; a structure for deoxyribose nucleic acid". Nature. 171 (4356): 737–8. Bibcode :1953Natur.171..737W. PMID 13054692 . doi :10.1038/171737a0 . * ^ Ferré-D'Amaré AR, Doudna JA (1999). " RNA
RNA
folds: insights from recent crystal structures". Annu Rev Biophys Biomol Struct. 28: 57–73. PMID 10410795 . doi :10.1146/annurev.biophys.28.1.57 . * ^ Gilbert, Walter G. 1980. DNA
DNA
Sequencing and Gene
Gene
Structure (Nobel Lecture) http://nobelprize.org/nobel_prizes/chemistry/laureates/1980/gilbert-lecture.html * ^ Sanger, Frederick. 1980. Determination of Nucleotide Sequences in DNA
DNA
(Nobel Lecture) http://nobelprize.org/nobel_prizes/chemistry/laureates/1980/sanger-lecture.html * ^ "Database resources of the National Center for Biotechnology Information" . Nucleic Acids Research. 42 (Database issue): D7–17. 2014. PMC 3965057  . PMID 24259429 . doi :10.1093/nar/gkt1146 .

BIBLIOGRAPHY

* Wolfram Saenger, Principles of Nucleic Acid Structure, 1984, Springer-Verlag New York Inc. * Bruce Alberts, Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, and Peter Walter Molecular Biology of the Cell, 2007, ISBN 978-0-8153-4105-5 . Fourth edition is available online through the NCBI Bookshelf: link * Jeremy M Berg, John L Tymoczko, and Lubert Stryer, Biochemistry 5th edition, 2002, W H Freeman. Available online through the NCBI Bookshelf: link * Astrid Sigel, Helmut Sigel and Roland K. O. Sigel, eds. (2012). Interplay between Metal Ions and Nucleic Acids. Metal Ions in Life Sciences. 10. Springer. ISBN 978-94-007-2171-5 . doi :10.1007/978-94-007-2172-2 . CS1 maint: Uses editors parameter (link )

EXTERNAL LINKS

* Interview with Aaron Klug,

.