Codon A sequence of three bases in mRNA

Codon A sequence of three bases in mRNA that specifies a particular amino acid in the translation process. 

C4 metabolism a photosynthetic pathway that produces a four-carbon molecule and avoids photorespiration in eukaryotic photo-synthesizing organisms coding strand the DNA strand that has the same base sequence as the RNA transcript (with thymine instead of uracil) codon a sequence of three nucleotides in mRNA that directs the incorporation of an amino acid during protein synthesis or acts as a start or stop signal coenzyme a small organic molecule required in the catalytic mechanisms of certain enzymes... 

A sequence of three bases in mRNA, called triplets, or codons, code for specific amino acids. Thus, the sequence CAG codes for glutamic acid, and GUC codes for valine. There are 64 (4 ) unique combinations of three-base sequences made from four bases. Some amino acids have more than one code. For example, leucine is coded for by six different codons UUA, UUG, CUU, CUC, CUA, and CUG. Methionine and tryptophan are the only amino acids that are coded by only one codon each. The same three-base sequence always codes for the same amino acid regardless of whether the organism is a bacterium or a human. 

Anticodon (Section 27 28) Sequence of three bases in a mole cule of tRNA that is complementary to the codon of mRNA for a particular ammo acid... 

This flow of information is dependent on the genetic code, which defines the relation between the sequence of bases in DNA (or its mRNA transcript) and the sequence of amino acids in a protein. The code is nearly the same in all organisms a sequence of three bases, called a codon, specifies an amino acid. Codons in mRNA are read sequentially by tRNA molecules, which serve as adaptors in protein synthesis. Protein synthesis takes place on ribosomes, which are complex assemblies of rRNAs and more than 50 kinds of proteins. 

A codon is a sequence of three bases (triplet) in mRNA (5 to 3 ) that spedfies, or corresponds to, a particular amino acid. During translation, the successive codons in an mRNA determine the sequence in which amino acids add to the growing polypeptide chain. 

Second, the tRNA must be able to recognize the appropriate codon on the mRNA that calls for that amino acid. This is mediated through a sequence of three bases called the anticodon, which is located at the bottom of the tRNA cloverleaf (refer to Figure 24.10). The anticodon sequence for each tRNA is complementary to the codon on the mRNA that specifies a particular amino acid. As you can see in Figure 24.11, the anticodon-codon complementary hydrogen bonding will bring the correct amino acid to the site of protein synthesis. 

The term codon refers to a sequence of three nucleotides in a messenger RNA (mRNA) that specifies the incorporation of a specific amino acid into a protein. The relationship between codons and the amino acids they code for is called the genetic code. The process of converting mRNA sequence information to the amino acid sequence of a protein is called translation. An anticodon is a complementary 3 base sequence in transfer RNA (tRNA). 

The anticodon, a sequence of three bases at the base of the clover-leaf. The bases in the anticodon are complementary to the bases of the codon of mRNA, and each species of tRNA binds specifically to one codon or, in some cases, two closely related codons for the same amino acid. 

Codon A sequence of three nucleic acid bases in DNA or mRNA that specify an individual amino acid. 

The specific ribonucleotide sequence in mRNA forms a message that determines the order in which amino acid residues are to be joined. Each "word," or codon, along the mRNA chain consists of a sequence of three ribonucleotides that is specific for a given amino add. For example, the series UUC on mRNA is a codon directing incorporation of the amino acid phenylalanine into the growing protein. Of the 43 = 64 possible triplets of the four bases in RNA, 61 code for specific amino acids and 3 code for chain termination, fable 28.1 shows the meaning of each codon. 

Translation, the second step in getting from a gene to a protein, takes place in the cytoplasm. The mRNA interacts with a specialized complex called a ribosome, which "reads" the sequence of mRNA bases. Each sequence of three bases, called a codon, usually codes for... 

The mRNA is bound to the smaller 30S subunit of the bacterial ribosome. The mRNA is a transcription of one of the genes of DNA, and carries the information as a series of three-base codons. The message is read (translated) in the 5 to 3 direction along the mRNA molecule. The aminoacyl-tRNA anticodon (UAC) allows binding via hydrogen bonding to the appropriate codon (AUG) on mRNA. In prokaryotes, the first amino acid encoded in the sequence is A-formylmethionine (fMet). Although the codon for initiation (A-formylmethionine) is the same as... 

Figure 25-28 Peptide-bond formation in protein biosynthesis showing how the amino-acid sequence is determined by complementary basepairing between messenger RNA and transfer RNA, The peptide chain is bound to tRNA, which is associated with mRNA through three bases in mRNA (codon) and three bases in tRNA (anticodon). In the diagram, the next codon A-A-G codes for lysine. Hence, Lys-tRNA associates with mRNA by codon-anticodon base-pairing and, under enzyme control, couples to the end of the peptide chain.

Transfer RNA (tRNA) transports the required amino acids from the cell s amino acid pool to the ribosome. Each type of amino acid can only be transported by its own specific tRNA molecule. The tRNA, together with its amino acid residue, binds to the mRNA already bound to the ribosome. It recognizes the point on the mRNA where it has to deliver its amino acid through the use of a consecutive sequence of three bases known as an anticodon, which is found on one of the loops of the tRNA (Figure 1.33(b)). This anticodon binds to the complementary codon of the mRNA. Consequently, the amino acids can only be delivered to specific points on the mRNA, which controls the order in which amino acid residues are added to the growing protein. This growth occurs from the N-terminal end of the protein. 

The nucleotide sequences of many tRNAs from a wide variety of organisms have been determined. All contain approximately 80 nucleotides, many of them of unusual structure (see Chap. 7). There is at least one tRNA corresponding to each amino acid, and while the sequences within individual tRNAs vary, they all form a common type of secondary structure (cloverleaf) in which the RNA chain folds back on itself to give a maximum amount of base pairing. One part of this structure is involved in the binding of an amino acid, and another part contains a sequence of three nucleotides complementary to one (or more) of the codons for this amino acid. This sequence of three nucleotides interacts with codons in the mRNA during the translational process. There are other features of the structure that are essential for the action of tRNA. 

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