Characteristics of the genetic codeTriplet: three bases specify each amino acid
Code word = 3 consecutive nucleotides
in the DNA
Codon = 3 consecutive nucleotides in mRNA
Anticodon = 3 consecutive nucleotides in tRNA that are complementary to a codon.Unambiguous: Each codon codes for the same amino acid in an organism.
Specificity: The genetic code is specific.The specific codon always codes for same amino acids. Degenerate:
The Striking features are the degeneracy of code i.e. 61 codons represent 20 amino acids.
More than one amino acid can code for the same amino acid.
Every amino acid except
Methionine is coded by several codons.
Often base of 3rd position is significant because four codons differing only in the 3rd base represent the same amino acids.
Comma less:
There are no spaces or punctuation between codons.
They are arranged in continues structure. Non-overlapping:
Adjacent bases belong to one and only 1 codon.
All codons are independent sets of 3 bases.
There is no overlapping.
Universal : The same coding dictionary is used by all organisms.
Co-linearity of gene and product:
The product of the gene is a protein specified by base
sequence.
High resolution genetic mapping technique has established that there is a linear correspondence in base sequence in gene and amino acid sequence in protein.
The genetic code has punctuation: contains start and stop signals.
There is a codon (AUG) which is the start a. Codes for formyl-methionine in prokaryotes and methionine in eukaryotes b. Codes for the first amino acid in all proteins.There are 3 codons (UAA, UAG, and UGA) that are stop codons a. When any one of these codons is reached during transcription, transcription stops b. These codons do not code for any amino acid.