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Molecular biology

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Molecular biology is the study of biology on a molecular level including the structure, function, and makeup of biologically important molecules such as DNA, RNA, and proteins.[1] Is the branch of biology that deals with the formation, structure, and function of macromolecules essential to life, such as nucleic acids and proteins, and especially with their role in cell replication and the transmission of genetic information.[2]

The central dogma of molecular biology

The central dogma of molecular biology was first stated by Francis Crick in 1958[3] and re-stated in a paper published in the journal Nature in August, 1970.[4] The central dogma of molecular biology states that

"The DNA acts as a template to replicate itself, and is also transcribed into RNA, and the RNA is translated into protein."[5]
DNA makes RNA makes protein.[6]

The central dogma states that once 'information' has passed into protein it cannot get out again. Transfer of information from protein to protein or from protein to nucleic acid is impossible. [7] All cells, from the simplest bacteria to humans, express their genetic information in this way - a fundamental principle of this dogma.[8] The finite automata below represents the central dogma:

Central dogma automata.png

There is special cases of transfers of biological sequential information. Reverse transcription, RNA replication and Direct translation from DNA to protein. The special transfers were indicated in the automata above (red arrows). In 1970 the first reports in Nature provided the first concrete evidence for the existence of transfer of information from RNA to DNA in retrovirus particles, the reverse transcription.[9] The impact of this discovery changed in some way the central dogma of molecular biology accepted for which information transfer is unidirectional. This discovery led to the name change of the RNA tumor viruses to retroviruses.[9] RNA replication is the copying of one RNA to another. Many viruses replicate this way. The enzymes that copy RNA to new RNA are called RNA-dependent RNA polymerases. A RNA virus need a RNA-dependent RNA polymerase to transcribe its genes into mRNA.[10]


Molecular biology was created in the 1940s by researchers inspired by metaphorical concepts of code, language and information.[11] In 1958, Francis Crick establishes the central dogma of molecular biology.[3]



Gel electrophoresis is a technique used to separate molecules of DNA, RNA, or protein. The DNA bands seen here are made visible by staining with Ethidium Bromide and viewing under ultra violet light.

DNA sequencing

DNA sequencing is the determination of the complete or part of the nucleotide sequence of a specific molecule of DNA.[12] This ability lies at the heart of the molecular biology revolution.[12]

Gel Electrophoresis

Linear DNA molecules become separate according to size when subjected to an eletric field through a gel matrix.[13] After electrophoresis is complete, the DNA molecules can be visualized by staining the gel with fluorescent dyes.[13]

Copying DNA: Polymerase chain reaction (PCR)

One way to copy DNA in large quantities is the PCR (polymerase chain reaction) method. PCR amplifies a short DNA fragment and produces a great amount of identical strings.[14] Single-target PCR is a robust and reliable technique for amplifying nucleic acids but it is still subject to many artifacts and environmental factors.[15]

Southern blotting

Invented and named by Edwin Southern, this method is used for probing for the presence of a specific DNA sequence within a DNA sample. It is a common method of using gene probes for looking at similarities, or differences, in the structure of a gene.[16]

Northern blotting

Is the simplest procedure to determine whether a gene is expressed in a sample but it really only confirm duplicate or greater differences in gene expression once the method is semi-quantitative.[17]

Western blotting

Western blotting, also called immunoblotting is a method used to track specific proteins in cell-free extracts. Proteins are first separated according to size by SDS-PAGE. The fractioned proteins are tranferred to a sheet of a nitrocellulose membrane and then exposed to a specific antibody.[18] Often, the antibodies are labeled with enzymes to allow detection.


  1. "Definition of Molecular biology". Retrieved 08-19-2012. 
  2. "molecular biology". Retrieved 8-19-2012. 
  3. 3.0 3.1 Crick, F.H.C. (1958). "On Protein Synthesis". Symp. Soc. Exp. Biol. XII: 139-163. 
  4. Crick, F.H.C. (August 1970). "Central dogma of molecular biology". Nature 227 (5258): 561–3. Bibcode 1970Natur.227..561C. PMID 4913914. 
  5. Gibas, Cynthia; Jambeck, Per (2001) (in portuguese). Desenvolvendo Bioinformática [Developing Bioinformatics Developing Skills]. Rio de Janeiro: Editora Campus. p. 22. ISBN 85-352-0923-9. 
  6. Bolsover, Stephen R.; Hyams, Jeremy S.; Shephard, Elizabeth A.; White, Hugh A.; Wiedemann, Claudia G (2004). Cell Biology. Hoboken, New Jersey: John Wiley & Sons. p. 39. ISBN 0-471-26393-1. 
  7. Waterman, Michael S (2000). Introduction to Computational Biology. Boca Raton, Florida: Chapman & Hall/CRC Press. p. 7. ISBN 0-412-99391-0. 
  8. Alberts, Bruce; Johnson, Alexander; Lewis, Julian; Raff, Martin; Roberts, Keith; Walter, Peter (2010) (in portuguese). Biologia Molecular da Célula [Molecular Biology of the Cell] (5th ed.). Porto Alegre: Artmed. p. 331. ISBN 978-85-363-2066-3. 
  9. 9.0 9.1 Flint, S. J.; Enquist, L. W.; Racaniello, V. R.; Skalka, A. M. Principles of Virology: Molecular Biology, Pathogenesis, and Control of Animal Viruses (2nd ed.). Washington, D.C.: ASM Press. p. 217-218. ISBN 1-55581-259-7. 
  10. Saunders, Venetia A.; Carter, John (2007). Virology: principles and applications. Chichester: John Wiley & Sons. pp. 74-75. ISBN 978-0-470-02387-7. 
  11. Konopka, Andrzej K.; Crabbe, M. James, ed. (2004). Compact Handbook of Computational Biology. New York: Marcel Dekker. p. 4. ISBN 0-8247-0982-9. 
  12. 12.0 12.1 Alphey, Luke (1997). DNA Sequencing:From Experimental Methods to Bioinformatics. New York: Springer/BIOS Scientific Publishers. pp. 1. ISBN 0-387-91509-5. 
  13. 13.0 13.1 Watson, James D.; Baker, Tania A.; Bell, Stephen P.; Gann, Alexander; Levine, Michael; Losick, Richard (2004). Molecular Biology of the Gene (5th ed.). San Francisco, CA: Pearson, Benjamin Cummings. p. 648. ISBN 0-8053-4635-X. 
  14. Pevzner, Pavel A. (2000). Computational Molecular Biology: An Algorithmic Approach. The MIT Press. p. 272-273. ISBN 0-262-16197-4. 
  15. Santalucia Jr., John (2007). "Physical Priciples and Visual-OMP Software for Optimal PCR Design". In Yuriev, Anton. PCR Primer Design. Totowa, New Jersey: Humana Press. p. 3-14. ISBN 978-1-58829-725-9. 
  16. Dale, Jeremy W.; Park, Simon F (2004). Molecular Genetics of Bacteria (4th ed.). San Francisco, CA: John Wiley & Sons. p. 64-66. ISBN 0-470-85084-1. 
  17. Gibson, Greg; Muse, Spencer V (2004). A Primer of Genome Science. Sunderland, MA: Sinauer Associates, Inc.. pp. 239-240. ISBN 0-87893-232-1. 
  18. Strachan, Tom; Read, Andrew (2011). Human Molecular Genetics (4th ed.). New York: Garland Science. p. 242-243. ISBN 978-0-815-34149-9.