Genetic Code

Estimated time: 6 minutes

CBSE: Class 12
CISCE: Class 12

Definition: Genetic Code

The genetic code is the specific sequence of nitrogenous bases in DNA that determines the order of amino acids in a protein.

CBSE: Class 12
Maharashtra State Board: Class 12
CISCE: Class 12

The genetic code is the relationship between the sequence of nucleotides in DNA/mRNA and the sequence of amino acids in a protein, thus controlling protein synthesis.
It is a triplet code in which three consecutive nucleotides (codon) specify one amino acid, giving a total of 64 codons (4³ combinations).
Out of 64 codons, 61 code for amino acids while 3 (UAA, UAG, UGA) act as stop codons, and AUG serves as the start codon coding for methionine.
The genetic code is degenerate, meaning more than one codon can code for the same amino acid, often due to variation at the third base (wobble position).
The triplet nature of the genetic code was confirmed by experiments such as frame-shift mutations by Francis Crick and the poly-U experiment by Marshall Nirenberg, which showed that UUU codes for phenylalanine.
Further decoding of codons was achieved using synthetic RNA techniques developed by Har Gobind Khorana, helping establish the full genetic code dictionary.
Changes (mutations) in the nucleotide sequence can alter amino acid sequences in proteins, showing that the genetic code directly determines protein structure and function.