Answer:
The correct answer is nitrogen base
Explanation:
The nucleotide sequence of one codon differ from that of another codon by the presence or absence of specific nitrogen base.The nucleotide sequence of different codons contain different nitrogen bases.
As a result change in genetic code result from the change in the nitrogen bases of the codons present in the genetic code.
In simple words change in single nitrogen base of a codon will change the entire codon.
