All are characteristics of genetic code?

All are characteristics of genetic code ?
a) Overlapping
b) Nonambiguous
c) Universal
d) Degeneracy
Correct Answer - A
Ans. is ‘a’ i.e., Overlapping
Characteristic 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 : -
    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.
    AGA and AGG serve as stop codon instead of coding for arginine.
  2. Unambiguous/Specific :- A particular 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 starting 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