Translation

Translation is the cellular process in which the genetic information carried by the DNA is decoded, using an RNA intermediate, into proteins. This process is also known as protein synthesis.

Deciphering the Genetic Code

There are two steps in the path from genes to proteins. In the first step, called transcription , the region of the double-stranded DNA corresponding to a specific gene is copied into an RNA molecule, called messenger RNA (mRNA), by an enzyme called RNA polymerase. In the second step, called translation, the mRNA directs the assembly of amino acids in a specific sequence to form a chain of amino acids called a polypeptide . This process is accomplished by ribosomes , special amino acid-bearing RNA molecules called transfer RNAs (tRNAs), and other translation factors. The newly synthesized polypeptides form proteins, which have functional and structural roles in cells. All proteins are synthesized by this process.

The precise order of amino acids assembled during translation is determined by the order of nucleotides in the mRNA. These nucleotides are a direct copy of the linear sequence of the nucleotides in one of the two complementary DNA strands, which have been transcribed using a code in which every three bases of the RNA specify an amino acid. DNA and RNA molecules both have directionality, which is indicated by reference to either the 5′ ("five prime") end or the 3′ ("three prime") end.

The code is always read in the 5′ to 3′ direction, using adjacent, non-overlapping three-base units called codons. Since there are four different nucleotides (also called bases) in RNA (abbreviated A, C, G, and U), there are sixty-four (4³) different codons, and each codon specifies a particular amino acid. There are only twenty different amino acids, however, so many of the amino acids can be specified by more than one codon, a circumstance that is known as degeneracy. The list of mRNA codons specific for a given amino acid is called the genetic code . The start signal, or initiation codon, for translating the mRNA is usually specified by an AUG, which codes for the amino acid methionine. Three codons (UAA, UGA, and UAG) do not specify an amino acid. Instead, these codons serve as stop signals to indicate that the end of the gene has been reached. During the translation process, they signal that no further amino acids are to be assembled.

The process of translation is carried out by ribosomes, which bind the mRNA and conduct a catalytic activity, called peptide bond formation, for joining the amino acids. The amino acids are carried to the ribosome by the tRNAs. Each tRNA has a specific amino acid attached to it and contains a nucleotide triplet called an anticodon. The anticodon recognizes a specific codon on the mRNA by pairing with it, using base-pairing rules like those used by DNA: A pairs with U and G pairs with C. For example, a tRNA with a UUU anticodon recognizes the AAA codon. The amino acid lysine is attached to this tRNA, so every time the ribosome "reads" an AAA codon, the lysine-bearing tRNA is brought in, base pairs via its anticodon to the codon, and delivers a lysine to the growing protein chain.

Mutations arise when one or more bases in the DNA is changed. When the mutated DNA is transcribed, the resulting mRNA will carry the same mutation. Then, when the mRNA is translated, the amino acid sequence of the resulting protein will be different from the original, or wild-type , sequence because the codons affected by the mutation will recruit the wrong amino acids. The resulting mutant protein may have neutral, harmful, or even beneficial effects on the individual. These changes are the basis for evolution.

Stages of Translation

The process of translation can be broken down into three stages. The first stage is initiation. In this step, a special "initiator" tRNA carrying the amino acid methionine binds to a special site on the small subunit of the ribosome (the ribosome is composed of two subunits, the small subunit and the large subunit). The mRNA is also loaded on, and positioned so that the initiation codon (usually AUG) is base paired with the anticodon of the initiator tRNA. The large subunit then binds to the small subunit. The resulting complex of ribosome, mRNA, and methionine-bearing initiator tRNA is called an initiation complex. Formation of this complex also requires a number of helper proteins called initiation factors.

The second stage is called chain elongation. During this stage, additional amino acids are progressively added. The methionine-bearing initiator tRNA sits on a site of the ribosome called the P (peptidyl) site. A new tRNA, bearing the next amino acid is base paired via its anticodon to the next codon of the mRNA, using a site called the A (acceptor) site. This new amino acid is then attached to the amino acid carried by the P site tRNA, forming a peptide bond. This enzymatic step is carried out by the ribosome, at a site called the peptidyl-transferase center.

The tRNA that has so far been attached to the amino acid in the P site is then released through the E (exit) site, and the new tRNA, now carrying both its own amino acid and the methionine moves into the P site. The mRNA also slides three bases to bring the next codon into position at the A site. A third tRNA, again carrying a specific amino acid and recognizing the third codon of the mRNA, moves into the A site, and the cycle is repeated. As these steps are continued, the mRNA slides along the ribosome, three bases at a time, and the peptide (amino acid) chain continues to grow. As with initiation, elongation requires helper proteins, called elongation factors. Energy is also required for peptide bond formation.

The final stage of translation is termination. The signal to stop adding amino acids to the polypeptide is a stop codon (UAA, UAG, or UGA), for which there is no partner tRNA. Rather, special proteins called release factors bind to the A site of the ribosome and trigger an enzymatic reaction by the ribosome. This reaction causes the ribosome to release the polypeptide and mRNA, ending the elongation process.

At a given time, more than one ribosome may be translating a single mRNA molecule. The resulting clusters of ribosomes, which resemble beads on a string, are called polysomes.

Recognition of Initiation Codons

Not all AUG codons serve as the site of initiation. Most AUGs are intended to code for methionines within the polypeptide chain. Therefore, in addition to the methionine-bearing initiator tRNA, another set of methionine-specific tRNAs are used for these internal AUG codons. The ribosome must be able to distinguish between these two kinds of AUG codons. In bacteria, additional information contained within the mRNA sequence immediately before the intended initiating AUG, called a Shine-Dalgarno sequence, helps the ribosome to recognize where it should start translating. Any AUG sequences on the 5′ side of the initiation codon are ignored. In eukaryotic cells, a different strategy is used to recognize the initiating AUG codon. The mRNA contains a special structure at its 5′ end, which helps the ribosome to attach and then to scan down the RNA molecule until it reaches the first AUG triplet. In bacteria and eukaryotes, AUG codons encountered during translation after initiation are recognized by a non-initiator methionine-bearing tRNA.

see also Genetic Code; Mutation; Nucleotide; Proteins; Reading Frame; Ribosome; RNA; Transcription.

Janice Zengel

Bibliography

Lewin, Benjamin. Genes VII. New York: Oxford University Press, 2000.

Translation

Translation is the process in which genetic information, carried by messenger RNA (mRNA), directs the synthesis of proteins from amino acids, whereby the primary structure of the protein is determined by the nucleotide sequence in the mRNA. Although there are some important differences between translation in bacteria and translation in eukaryotic cells the overall process is similar. Essentially, the same type of translational control mechanisms that exist in eukaryotic cells do not exist in bacteria.

A molecule known as the ribosome is the site of the protein synthesis . The ribosome is protein bound to a second species of RNA known as ribosomal RNA (rRNA). Several ribosomes may attach to a single mRNA molecule, so that many polypeptide chains are synthesized from the same mRNA. The ribosome binds to a very specific region of the mRNA called the promoter region. The promoter is upstream of the sequence that will be translated into protein.

The nucleotide sequence on the mRNA is translated into the amino acid sequence of a protein by adaptor molecules composed of a third type of RNA known as transfer RNAs (tRNAs). There are many different species of tRNAs, with each species binding a particular type of amino acid. In protein synthesis, the nucleotide sequence on the mRNA does not specify an amino acid directly, rather, it specifies a particular species of tRNA. Complementary tRNAs match up on the strand of mRNA every three bases and add an amino acid onto the lengthening protein chain. The three base sequence on the mRNA are known as "codons," while the complementary sequence on the tRNA are the "anti-codons."

The ribosomal RNA has two subunits, a large subunit and a small subunit. When the small subunit encounters the mRNA, the process of translation to protein begins. There are two sites in the large subunit, an "A" site, and a "P" site. The start signal for translation is the codon ATG that codes for methionine. A tRNA charged with methionine binds to the translation start signal. After the first tRNA bearing the amino acid appears in the "A" site, the ribosome shifts so that the tRNA is now in the "P" site. A new tRNA molecule corresponding to the codon of the mRNA enters the "A" site. A peptide bond is formed between the amino acid brought in by the second tRNA and the amino acid carried by the first tRNA. The first tRNA is now released and the ribosome again shifts. The second tRNA bearing two amino acids is now in the "P" site, and a third tRNA can now bind to the "A" site. The process of the tRNA binding to the mRNA aligns the amino acids in a specific order. This long chain of amino acids constitutes a protein. Therefore, the sequence of nucleotides on the mRNA molecule directs the order of the amino acids in a given protein. The process of adding amino acids to the growing chain occurs along the length of the mRNA until the ribosome comes to a sequence of bases that is known as a "stop codon." When that happens, no tRNA binds to the empty "A" site. This is the signal for the ribosome to release the polypeptide chain and the mRNA.

Bacterial ribosomes are smaller than eukaryotic ribosomes. In some cases, bacterial ribosomes contain less than have the total protein found in eukaryotic ribosomes. Bacteria also respond to fewer initiation factors than do eukaryotic cells.

After being released from the tRNA, some proteins may undergo post-translational modifications. They may be cleaved by a proteolytic (protein cutting) enzyme at a specific site. Alternatively, they may have some of their amino acids biochemically modified. After such modifications, the polypeptide forms into its native shape and starts acting as a functional protein in the cell.

There are four different nucleotides, A, U, G and T. If they are taken three at a time (to specify a codon, and thus, indirectly specify an amino acid), 64 codons could be specified. However, there are only 20 different amino acids. Therefore, several triplets code for the same amino acid; for example UAU and UAC both code for the amino acid tyrosine. In addition, some codons do not code for amino acids, but code for polypeptide chain initiation and termination. The genetic code is non-overlapping, i.e., the nucleotide in one codon is never part of the adjacent codon. The code also seems to be universal in all living organisms.

See also Cell cycle (prokaryotic), genetic regulation of; Chromosomes, prokaryotic; Cytoplasm, prokaryotic; Genetic regulation of prokaryotic cells; Molecular biology and molecular genetics; Protein synthesis; Proteins and enzymes; Ribonucleic acid (RNA)

TRANSLATION

There are a large number of occurrences of the verb übersetzen ("to translate") and the nounÜbersetzung ("translation") in Freud's work, indicative of his interest in translation, although the terms had no specific conceptual value for him within the field of psychoanalysis. However, non-German readers should bear in mind the proximity in German ofÜbersetzung and Übertragung ("transference"). What psychoanalysts refer to as "transference" is, in German, also a translation, a carrying over.

Freud's interest in translation was manifest early in his career: while doing his military service he translated an essay by John Stuart Mill and, on his return from his stay at the Salpêtrière, impressed by Charcot's clinical method, he translated two of the Charcot's main works, as well as two works by Bernheim, which he felt were essential for a scientific understanding of hysteria and the use of therapeutic methods in hypnosis. For Freud the experience of translation was contemporary with his discovery of psychoanalysis as a therapeutic practice. Ernest Jones emphasized Freud's gifts as a translator (Pollak Cornillot, 1990). It should come as no surprise, therefore, to find that translation infiltrated his thought as a metaphor for a large number of psychic processes.

In his earliest writings and with the appearance of the concept of repression, translation, in its primary sense of "to bring over," became a way of picturing the transformation of those psychic contents reaching consciousness, repression being thus defined (Freud to Fliess, December 6, 1896) as a "defect of translation," an absence of conscious expression. The work of dream interpretation likewise resembles a translation of the language of the unconscious into the language of consciousness, of the remembered dream content into its hidden sense: "Interpreting a dream consists in translating the manifest content of the dream into the latent dream-thoughts, in undoing the distortion which the dream-thoughts have had to submit to from the censorship of the resistance" (1907a, p. 59). But at the same time Freud cautioned against the tendency to overestimate the importance of symbols and reduce the work of dream translation to the mere decoding of symbols, and to ignore the ideas that present themselves to the mind of the dreamer during analysis. Finding the hidden meaning was more complex than the simple transliteration of the signs of the unconscious system into the signs of the conscious one. Elsewhere (1918b [1914]), Freud uses the term translation more generically, to designate the psychoanalyst's interpretation of a psychic phenomenon: for example, the fear of being eaten by the wolf "is translated" into the fear of being raped by the father. More recently André Green (1997/2000) has rediscovered the richness of the "hypothesis of translation" present throughout Freud's work.

MichÈle Pollak Cornillot

See also: Biblioteca Nueva de Madrid (Freud, S., Obras completas ); France; Interpretation; Opere (writings of Sigmund Freud); Standard Edition of the Complete Psychological Works of Sigmund Freud ; Symbol.

Bibliography

Freud, Sigmund. (1907a). Delusions and dreams in Jensen's "Gradiva." SE, 9: 1-95.

——. (1918b [1914]). From the history of an infantile neurosis. SE, 17: 1-122.

Green, André. (2000). The chains of eros: The sexual in psychoanalysis (Luke Thurston, Trans.). London: Rebus. (Original work published 1997)

Mahony, Patrick. (1980). Toward the understanding of translation in psychoanalysis. Journal of the American Psychoanalytic Association, 28, 461-473.

Mijolla, Alain de. (1991). L'édition en français des "Œuvres" de Freud avant 1940. Autour de quelques documents nouveaux. Revue internationale d 'histoire de la psychanalyse, 4, 209-270.

Pollak Cornillot, Michèle. (1990). Freud traducteur. Introductionà la traduction des œuvres de Freud. Doctoral dissertation, Université René-Descartes, Paris.

Further Reading

Amati-Mehler, Jacqueline, et al. (1993). The babel of the unconscious. Mother tongue and foreign languages in the psychoanalytic dimension. Madison, CT: International Universities Press.

TRANSLATION The restatement of the forms of one LANGUAGE in another: the chief means of exchanging information between different language communities. Translation is a fundamental yet often overlooked element in life and has played a decisive part in the development of languages like English, especially by promoting the flow of ideas and the spread of the literary forms in which they have been expressed: for example, Homeric poetry from ancient Greece and the Bible translated from Hebrew and Greek. As the Canadian historian of translation Louis Kelly has observed, ‘Western Europe owes its civilization to translators’ (1979). Five distinctions are commonly made when discussing translation, none of which represent absolute positions, but rather end-points in an appropriate continuum:

1. Translating and interpreting.

Written translation can be distinguished from oral translation or interpreting, which came first, as for example in military and diplomatic exchanges. However, because of its relative permanence and lasting influence on the transmission of culture and technology, written translation has traditionally been considered more important. Professional interpreting takes two forms: simultaneous interpreting (at international conferences, etc.) and consecutive interpreting (in court, at diplomatic gatherings, in business transactions, etc.).

2. Word-for-word and free translation.

Languages do not match neatly in the way they form messages. Depending on the level at which translation equivalence can be established (word with word, phrase with phrase, word with phrase, etc.) translations can be more literal (that is, one-to-one at the level of words), or free (restatement of the message regardless of formal correspondence).

3. Literary and technical translation.

Depending on the type of discourse translated, a distinction is often made between literary translation (of aesthetic, imaginative, fictional texts) and technical translation (of workaday, pragmatic, nonfictional texts). However, boundary lines between them are sometimes difficult to draw, as in the translation of the Bible (which is currently available in over 2,000 languages): for example, the drama of the Book of Job and the listing of laws in Leviticus.

4. Professional and pedagogical translation.

A distinction can be made between translation as a vocation or trade (working for a client) and translation as an exercise in the process of language learning (working for a teacher). It has been argued that traditional grammar—translation tasks in school do not constitute a suitable training for translating as such.

5. Human and machine translation.

The high cost of professional translating and interpreting has encouraged institutional investment in experiments with largescale electronic translation and dictionary systems. However, fully automatic translation of high quality still seems still to be a long way off.

Translation and publishing

Much of the world's publishing depends on translation, although the centrality of the translator's role is often only minimally indicated in the credits of particular works. Thousands of translators and interpreters around the world continue to perform essential tasks in often less-than-ideal conditions. By the early 1970s, close to half of the world's book production was made up of translations, the chief source languages being English, French, Russian, German, Spanish, and Italian, the chief target languages German, Russian, Spanish, English, Japanese, and French. Because of worldwide demand for translation of all kinds, the 20c has been referred to as ‘the age of translation’.

trans·late / transˈlāt; tranz-/ • v. [tr.] 1. express the sense of (words or text) in another language: the German original has been translated into English. ∎  [intr.] be expressed or be capable of being expressed in another language: shiatsu literally translates as “finger pressure.” ∎  (translate something into/translate into) convert or be converted into (another form or medium): [tr.] few of Shakespeare's other works have been translated into ballets. 2. move from one place or condition to another: she had been translated from familiar surroundings to a foreign court. ∎  formal move (a bishop) to another see or pastoral charge. ∎  formal remove (a saint's relics) to another place. ∎  poetic/lit. convey (someone, typically still alive) to heaven. ∎  Biol. convert (a sequence of nucleotides in messenger RNA) to an amino-acid sequence in a protein or polypeptide during synthesis. 3. Physics cause (a body) to move so that all its parts travel in the same direction, without rotation or change of shape. ∎  Math. transform (a geometric figure) in an analogous way. DERIVATIVES: trans·lat·a·bil·i·ty / ˌtransˌlātəˈbilətē; ˌtranz-/ n. trans·lat·a·ble adj.

trans·la·tion / transˈlāshən; tranz-/ • n. 1. the process of translating words or text from one language into another: Constantine's translation of Arabic texts into Latin. ∎  a written or spoken rendering of the meaning of a word, speech, book, or other text, in another language: a German translation of Oscar Wilde's play a term for which there is no adequate English translation. ∎  the conversion of something from one form or medium into another: the translation of research findings into clinical practice. ∎  Biol. the process by which a sequence of nucleotide triplets in a messenger RNA molecule gives rise to a specific sequence of amino acids during synthesis of a polypeptide or protein. 2. formal or technical the process of moving something from one place to another: the translation of the relics of St. Thomas of Canterbury. ∎  Math. movement of a body from one point of space to another such that every point of the body moves in the same direction and over the same distance, without any rotation, reflection, or change in size. DERIVATIVES: trans·la·tion·al / -shənl/ adj. trans·la·tion·al·ly / -shənl-ē/ adv.

translation The process in living cells in which the genetic information encoded in messenger RNA (mRNA) in the form of a sequence of nucleotide triplets (codons) is translated into a sequence of amino acids in a polypeptide chain during protein synthesis (see illustration). Translation takes place on ribosomes in the cell cytoplasm (see initiation factor). The ribosomes move along the mRNA `reading' each codon in turn. Molecules of transfer RNA (tRNA), each bearing a particular amino acid, are brought to their correct positions along the mRNA molecule: base pairing occurs between the bases of the codons and the complementary base triplets of tRNA (see anticodon). In this way amino acids are assembled in the correct sequence to form the polypeptide chain (see elongation). Translation is terminated by the release factor.

translation. In ecclesiastical usage:
1. the transference of the relics of a saint either from their original place of burial into an altar tomb or shrine or from one shrine to another;

2. the transference to a different day of a feast when the season (e.g. Holy Week) prohibits its observance, or when a feast of higher rank occurs on the same day;

3. the transference of a cleric from one ecclesiastical office to another, especially of a bishop from one see to another.

translation The polymerization of amino acids into a polypeptide chain whose structure is determined genetically. This process occurs on a ribosome and involves several small proteins, m-RNA, and t-RNA. The sequence of amino acids in the chain is specified by that of the nucleotides in the m-RNA (these being read as codons, i.e. in groups of three), and this in turn follows the sequence of nucleotides in the DNA.

translation The conversion of the base sequence in m-RNA into an amino-acid sequence in a polypeptide chain by a process that occurs on a ribosome and involves several small proteins, m-RNA, and t-RNA. The sequence of amino acids in the chain is specified by that of the nucleotides in the m-RNA (these being read as codons, i.e. in groups of three), and this in turn follows the sequence of nucleotides in the DNA.

translate
A. remove from one place to another;

B. turn from one language into another. XIII. prob. first in pp. translate — L. translātus, functioning as pp. of transferre TRANSFER; but perh. reinforced by OF. translater, medL. translātāre.
So translation, translator XIV. — OF. or L.

translation The production of a polypeptide sequence of amino acids from the information encoded in the nucleotide sequence of messenger-RNA. The process takes place at the ribosome.

translation (tranz-lay-shŏn) n. (in cell biology) the manufacture of proteins in a cell, which takes place at the ribosomes. See messenger RNA, transfer RNA.

translation (protocol translation) See internetworking.

translation See COILING.

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