What are the characteristics of genetic code?

1, directionality, codon refers to the base sequence of mRNA molecule, and its reading direction is consistent with the synthesis direction or coding direction of mRNA, that is, from 5' end to 3' end.

2. continuity. The reading direction of mRNA is from 5' end to 3' end, and there is no nucleotide separation between the two codons. Insertion, deletion and overlap of bases in mRNA chain will lead to frameshift mutation.

Degeneracy means that an amino acid has two or more codons. The change of the third base of codon often does not affect the translation of amino acids.

4. Swing, when the codon on mRNA is paired with the anti-codon on transfer RNA(tRNA)J, the principle of base complementary pairing is observed in most cases, but there may be loose pairing, especially when the third base of codon is paired with the first base of anti-codon, which is called swing pairing.

5, universality, a set of codes for protein biosynthesis, from prokaryotes to humans. But a few exceptions have been found, such as mitochondria of animal cells and chloroplasts of plant cells.

Extended data:

Although the genetic codes of different lives are very consistent, there are also non-standard genetic codes. Mitochondria, known as the "cell energy factory", have several differences from the standard genetic code. Even the mitochondria of different organisms have different genetic codes. Mycoplasma will convert UGA into tryptophan.

Ciliates translate UAG (sometimes UAA) into glutamine (as do some green algae) or UGA into cysteine. Some yeasts will translate GUG into serine. In some rare cases, the start codon of some protein is not AUG.

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