Pre- or post-mRNA translation may indirectly introduce errors of protein synthesis during transcription and posttranslational processing. Nevertheless, mistranslation universally occurs. Accordingly, optimizing of tRNA wobble and codon usage in mRNA can substantially enhance translation efficiency and accuracy. The efficiency of mRNA decoding machinery is also essentially regulated by codon usage bias that is distinguished by over- or underrepresented synonymous codons. Besides the abundance of tRNA species, mRNA translation is regulated by nearly 100 epigenetic tRNA modifications, especially at the wobble position. Translational decoding of the mRNA codons is constrained by factors during codon–anticodon recognition and often constitutes the rate-limiting step during protein synthesis. In parallel, the numbers of certain amino acid–specified tRNAs (based on recognition of anticodons) also vary from two to six box tRNA sets. For each amino acid, the number of codon usage varies from two to six according to codon degeneracy. The resulting redundancies in the genetic code attribute to synonymous codons, which involve wobbling at position 3. In the canonical interpretation, 61 aminoacyl-tRNAs and 3 suppress tRNAs decode 64 triplet codons that specify 20 amino acids. The discrepancy between error rates in DNA replication and mRNA translation may partially relate to the fact that DNA replication occurs at the level of individual nucleotides (involving 4 1 = 4 possible permutations), whereas the translation machinery interprets mRNA codons in triplets (involving 4 3 = 64 possible permutations). The general error rates of genomic replication (about 10 −8) are estimated to be approximately 10,000-fold lower than those of protein synthesis (about 10 −4), and thus in most instances mRNA translation is the key process contributing to inaccuracy of the cellular proteome. However, the translation machinery is not always perfect, and errors in the amino acid composition may occur. Deciphering mRNA codons by transfer RNAs (tRNAs) in the ribosome involves Watson-Crick base pairing. The latter process is executed by the ribosome, which constitutes the translation machinery that produces the cellular proteome by decoding mRNAs. The maximum number of components in the DECODE function, including expr, searches, results, and default, is 255.In all living organisms, DNA is transcribed into RNA, and RNA is translated into protein. If expr is null, then Oracle returns the result of the first search that is also null. In a DECODE function, Oracle considers two nulls to be equivalent. If the first result has the data type CHAR or if the first result is null, then Oracle converts the return value to the data type VARCHAR2. Oracle automatically converts the return value to the same data type as the first result. Oracle automatically converts expr and each search value to the data type of the first search value before comparing. Consequently, Oracle never evaluates a search if a previous search is equal to expr. The database evaluates each search value only before comparing it to expr, rather than evaluating all search values before comparing any of them with expr. Oracle Database uses short-circuit evaluation. The search, result, and default values can be derived from expressions. If the first search-result pair are numeric, then Oracle compares all search-result expressions and the first expr to determine the argument with the highest numeric precedence, implicitly converts the remaining arguments to that data type, and returns that data type. The string returned is of VARCHAR2 data type and is in the same character set as the first result parameter. expr, search, and result can be any of the data types CHAR, VARCHAR2, NCHAR, or NVARCHAR2. If expr and search are character data, then Oracle compares them using nonpadded comparison semantics. The arguments can be any of the numeric types ( NUMBER, BINARY_FLOAT, or BINARY_DOUBLE) or character types. If default is omitted, then Oracle returns null. If no match is found, then Oracle returns default. If expr is equal to a search, then Oracle Database returns the corresponding result. DECODE compares expr to each search value one by one.
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