Question

What is the anticodon for CCA?

Answer 1

Hint: Genetic code is the genetic information present in the nucleotide sequences of DNA with three consecutive nucleotides functioning as a codon in a non-overlapping fashion. The genetic vocabulary consists of 64 codons. Each codon contains a message for the construction of polypeptide chains. Genetic code is, therefore, also defined as a correspondence between the sequence of amino acids in polypeptides and the nucleotide sequence in DNA. The genetic code was deciphered by the efforts of a number of workers like Crick, Ochoa Nirenberg, Khorana and Matthei. Sovero Ochoa discovered polynucleotide polymerase (Ochoa enzyme for template independent polymerisation of nucleotides. Khorana synthesised RNAs with a defined combination of nucleotides (homopolymers, copolymers). Nirenberg could synthesise protein in cell free systems.

Complete answer:
Characteristics of Genetic code:
1. Triplet Nature. Genetic code is a triplet code where three adjacent nitrogen bases specify one amino acid e.g., UGG for tryptophan, AUG for methionine.
2. Non-overlapping. Three successive nucleotides or nitrogen bases code for only one amino acid. None of these nitrogen bases become part of any other codon.
3. Commaless. Genetic code does not possess punctuation. Once Started, it is continuous till the end.
4. Specificity or Unambiguity. Genetic code is specific and unambiguous because a single codon codes for only one amino acid.
5. Universality: Same codon specifies the same amino acid from bacteria to human beings. Exceptions: However, it occurs in some mitochondrial and viral genes.
Number: The total number of codons is 64. Most of them specify amino acids with some functioning as start and stop signals.
Initiation Codons: They signal the initiation of polypeptide synthesis. Their number is two, AUG or methionine codon and GUG or valine codon.
Termination Codons: These are stop signals, which means when encountered to cause termination of polypeptide synthesis. Termination codons are also called nonsense codons because they do not specify any amino acid. The termination codons are UAA (ochre), UAG (amber) and UGA (opal).
Polarity: The code is read in the direction of 5’ to 3’. Usually the code present on mRNA is recognized as a genetic code. The complementary code present on template DNA is not considered. If DNA code is to be mentioned, the same is the one which is present on the sense strand (complementary to the template strand). Here the code is similar to that of mRNA with U replaced by T.
Degeneracy: Out of 64 codons only 3 codons signify stop signals. Only two codons specify a single amino acid. Three amino acids have 6 codons each. 5 amino acids with 4 codons, one amino acid with 3 codons and 9 amino acids are specified by two codons each.

Thus the anticodon for CCA is GGU.

Note:
Some other characteristics of Genetic code: Collinearity. The sequence of amino acids present in polypeptide corresponds to a sequence of nitrogen bases of DNA with three successive nitrogen bases forming a single codon. A change in any codon due to addition, deletion or replacement of nucleotides results in change in the reading of genetic code as well as incorporation of amino acids in polypeptide. Related Codons. Amino acids having similar properties are also specified by related codons, e.g., aromatic amino acids tryptophan-UGG, tyrosine-UAU, UAC. Phenylalanine-UUU, UUC.