Genetic Code: 

Genetic means: Related to Gene,  and Code means: Hidden. 

Genetic code is discovered by Marshall Nirenberg. 

In 1961, Francis Crick and co-workers brought the concept of the codon. However, it changed into Marshall Nirenberg and co-people who deciphered the genetic code. They confirmed that 4 nucleotide bases – A (adenine), U (uracil), G (guanine) and C (cytosine) ─ shape codons of various base combos that code for all 20 amino acids throughout protein synthesis.

The sequence of nucleotides (nitrogenous bases ) in the DNA molecules  which encloses information of protein synthesis is called Genetic Code. 

DNA is the genetic material of all living organism. It stores information for protein synthesis. 

But problem was that : Only four types of Nucleotides bases to specify 20 Amino acids. 

• If one Nucleotide base  translate for amino acid only four amino acid could be specified i.e.  1×4 =4 

• If two bases code for an Amino acid then  4×4= 16  

           Triplet Code System 

• If three bases specify an Amino acid there  can be 64 possible combinations forms which are more than enough for 20 Amino acids. 

                                4×4×4= 64        

• Of which 61= Sense Code( having information for specific protein). 

                      1( Start Codon ) AUG 

3 Non Sense Codes (having no information ) Stop Codons= UAA, UAG, UGA.

                Start / Stop Codon 

Stop Codon: Out of 64 Codons, three codons i.e. UAA, UAG, and UGA do not code for any amino acid and these are known as Stop Codons also known as Non/Sense termination codons. 

They are Usually present at the end of gene.

Start Codon: Every gene starts with initiation  codon AUG called start codon. 

Which encodes the Amino acid Methionine. 

          Sequence reading frame 

In molecular biology, a reading frame is a way of dividing the sequence of nucleotides in a nucleic acid ( DNA or RNA) molecule in to a set of consecutive, non-overlapping triplets. Where these triplets equates to amino acids or stop signals during translation, they are called codons. 

           Characteristic of Genetic Code 

• Code is degenerate more than one codon for amino acid, like CAU, UAA( Histidine). 

• Code is Non-overlapping : have end to end sequence ( TAC ACC GCC GGT ATC ).

• Code is Universal : Same for all living organism . 

• The genetic code has sixty four codons. Out of these, sixty one codons code for 20 distinctive amino acids. However, not one of the codons codes for a couple of amino acid. In short, every codon codes most effective for one amino acid. This truly shows that the genetic code is non-ambiguous. 

• It is thought that the genetic code is comma less. In different words, the codons are non-stop and there aren't  any demarcation strains among codons.