A codon codes for a single amino acid. This characteristic is called ?
Ans. is 'b' i.e., Unambiguous Characteristics of genetic codes Genetic codes have following characteristics ? 1) Universal :- Each codon specifically codes for same amino acid in all species, e.g. UCA codes for serine and CCA codes for proline in all organisms. That means specificity of codon has been conserved from very early stages of evolution. Exception to the universality of genetic coder are found in human mitochondria, where the code :- a UGA codes for tryptophan instead of serving as a stop codon. AUA codes for methionine instead of isoleucine. CUA codes for threonine instead of leucine. LI AGA and AGG serve as stop codon instead of coding for arginine. 2) Unambiguous/Specific :- A paicular codon always codes for the same amino acid. For example CCU always codes for proline and UGG always codes for tryptophan. 3) Degeneracy/Redundancy :- A given amino acid may have more than one codon. For example, CCU, CCC, CCA and CCG all four codons code for proline. Therefore, there are 61 codons for 20 amino acids. 4) Stop or termination or nonsense codons:- Three of the 64 possible nucleotide triplets UAA (amber), UAG (Ochre) and UGA (opal) do not code for any amino acid. They are called nonsense codons that normally signal termination of polypeptide chains. Thus, though there are 64 possible triplet codons, only 61 codes for 20 amino acids (as remaining three are non-sense codons). 5) Non overlapping and nonpuntate (Comma less) :- During translation, the code is read sequentially, without spacer bases, from a fixed staing point, as a continuous sequence of bases, taken 3 at a time, e.g. AUGCUA GACUUU is read as AUG/CUA/GAC/UUU without "ponctation" (coma) between codons.
Non-overlapping
Unambiguous
Non-punctate
Degeneracy