The nucleotides comes from messenger RNA or mRNA during protein synthesis.
Explanation:
Protein synthesis is the final step of central dogma of molecular biology.During translation or protein biosynthesis the 3 consecutive nucleotides of substrate mRNA act as codons and each codon codes for speficic amino acids.For example AUG codes for amino acid methionine.
The nucleotides during protein synthesis comes from Messenger RNA or mRNA which is synthesized from template DNA strand in the nucleus during transcription.
