Which is not a salient feature of genetic code ?

Options

A. Ambiguous
B. Universal
C. Specific
D. Degenerate

Answer

A

Explanation

Salient features of genetic code :
(i) The codon is triplet. 61 codons code for amino acids and 3 codons do not code for any amino acids, hence they function as storp codons or non-sence codons/termination codons. These are UAA (Ochre), UAG (Amber) and UGA (Opal).
(ii) One codon codes for only amino acid, hence, it is unambiguous and specific.
(iii) Some amino acids are coded by more than one codon, hence the code is degenerate or redundant. This property is called degeneracy or redundancy.
`**" "`61 codons code for 20 amino acids, this is degeneracy.
`**" "`Only methionine (AUG) and tryptophan (UGG) are specified by single codons.
`**" "`In degenerate codons, mostly the first two bases are similar while third is different.
`**" "`Degeneracy is due to the third base of codon.
`**" "`Since third nitrogen base has no effect on coding it is called Wobble hypothesis (Proposed by Crick-1966).
`**" "`Wobble hypothesis establishes economy is tRNA molecules.
(iv) The codon is read in mRNA in a contiguous fashion. there are no punctuations.
`**" "`Codons are commaless.
(v) The code is nearly universal for example, from bacteria to human UUU would code for phenylalanine (phe). Some exceptions to this rule have been found in mitochondrial codons, and in some protozoans.
`**" "`In human mitrochondria AUA codes for methionine.
(vi) AUG has dual functions.
`**" "`It codes for Methionine (met), and it also act as initiator codon.