<unk>  (abbreviated<unk> , first hypothesized by Francis Crick, is a small<unk>  chain (73-93 nucleotides) that<unk> s a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation. It has a 3' terminal site for amino acid attachment. This covalent linkage is catalyzed by an aminoacyl<unk>  synthetase. It also contains a three base region called the anticodon that can base pair to the corresponding three base codon region on mRNA. Each type of<unk>  molecule can be attached to only one type of amino acid, but because the genetic code contains multiple codons that specify the same amino acid,<unk>  molecules bearing different anticodons may also carry the same amino acid.<unk>  has primary structure, secondary structure (usually visualized as the cloverleaf structure), and tertiary structure (all<unk> s have a similar L-shaped 3D structure that allows them to fit into the P and A sites of the ribosome).
An anticodon is a unit made up of three nucleotides that correspond to the three bases of the codon on the mRNA. Each<unk>  contains a specific anticodon triplet sequence that can base-pair to one or more codons for an amino acid. For example, one codon for lysine is AAA; the anticodon of a lysine<unk>  might be UUU. Some anticodons can pair with more than one codon due to a phenomenon known as wobble base pairing. Frequently, the first nucleotide of the anticodon is one of two not found on mRNA: inosine and pseudouridine, which can hydrogen bond to more than one base in the corresponding codon position. In the genetic code, it is common for a single amino acid to occupy all four third-position possibilities; for example, the amino acid glycine is coded for by the codon sequences GGU, GGC, GGA, and GGG.
To provide a one-to-one correspondence between<unk>  molecules and codons that specify amino acids, 61<unk>  molecules would be required per cell. However, many cells contain fewer than 61 types of<unk> s because the wobble base is capable of binding to several, though not necessarily all, of the codons that specify a particular amino acid.
Aminoacylation is the process of adding an aminoacyl group to a compound. It produces<unk>  molecules with their CCA 3' ends covalently linked to an amino acid.
Each<unk>  is aminoacylated (or charged) with a specific amino acid by an aminoacyl<unk>  synthetase.  There is normally a single aminoacyl<unk>  synthetase for each amino acid, despite the fact that there can be more than one<unk> , and more than one anticodon, for an amino acid.  Recognition of the appropriate<unk>  by the synthetases is not mediated solely by the anticodon, and the acceptor stem often plays a prominent role.
Reaction:
The ribosome has three binding sites for<unk>  molecules: the A, P and E sites. During translation the A site binds an incoming aminoacyl-tRNA as directed by the codon currently occupying this site. This codon specifies the next amino acid to be added to the growing peptide chain. The A site is only working after the first aminoacy-tRNA has attached to the P site. The P-site codon is occupied by peptdyl-tRNA that is a<unk>  with multiple amino acids attached as a long chain. The P site is actually the first to bind to aminoacyl<unk> . This<unk>  in the P site carries the chain of amino acids that has already been synthesized. The E site is occupied by the empty<unk>  as it is about to exit the ribosome.
Transfer RNA
Capsid
Viral vector
Viral envelope
Membrane fusion protein
Ribozyme
Vector
Vector 