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For example, if there were two bases per codon, then only 16 amino acids could be coded for (4²=16). Because at least 21 codes are required (20 amino acids plus stop) and the next largest number of bases is three, then 4³ gives 64 possible codons, meaning that some degeneracy must exist.
Depiction of one common way to clone a site-directed mutagenesis library (i.e., using degenerate oligos). The gene of interest is PCRed with oligos that contain a region that is perfectly complementary to the template (blue), and one that differs from the template by one or more nucleotides (red).
However, it is now agreed that the genetic code evolves, [22] resulting in discrepancies in how a codon is translated depending on the genetic source. [21] [22] For example, in 1981, it was discovered that the use of codons AUA, UGA, AGA and AGG by the coding system in mammalian mitochondria differed from the universal code. [21]
For example, "AA" is assigned to blue, "AC" is assigned to green, and so on for all 16 unique pairs. During sequencing, each base in the template is sequenced twice, and the resulting data are decoded according to this scheme.
Examples of degeneracy are found in the genetic code, when many different nucleotide sequences encode the same polypeptide; in protein folding, when different polypeptides fold to be structurally and functionally equivalent; in protein functions, when overlapping binding functions and similar catalytic specificities are observed; in metabolism, when multiple, parallel biosynthetic and ...
These "rate-distortion" models [107] suggest that the genetic code originated as a result of the interplay of the three conflicting evolutionary forces: the needs for diverse amino acids, [108] for error-tolerance [103] and for minimal resource cost. The code emerges at a transition when the mapping of codons to amino acids becomes nonrandom.
Template: Acids and bases. 25 languages. ... Download QR code; Print/export Download as PDF; Printable version; In other projects Wikidata item;
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