The genetic code, which represents the instructions for building proteins, is composed of a series of nucleotide triplets called codons. Each codon consists of three nucleotide bases. There are four different nucleotide bases in DNA: adenine (A), cytosine (C), guanine (G), and thymine (T).
The code needs four nucleotide bases to provide enough unique combinations for coding all twenty amino acids that make up proteins. There are 20 different amino acids commonly found in proteins, so if there were only two nucleotide bases, we would only have 2^2 (four) possible codons, which would not be enough to code for all 20 amino acids.
With three bases per codon, there are 4^3 (64) possible combinations of nucleotides. This provides enough variety for coding the 20 amino acids, allowing for redundancy in the genetic code. Some amino acids have more than one codon that codes for them, referred to as degeneracy in the genetic code.
This redundancy and the larger number of possible codons are important for preventing errors during protein synthesis. If there was only a one-to-one correspondence between nucleotides and amino acids, any mutation or error in a single nucleotide would result in an incorrect amino acid being incorporated into the protein. The redundancy allows for some tolerance to mutations, as multiple codons can specify the same amino acid, reducing the impact of errors.
why four neuclotide bases are needed to make 3 base codon
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