Answer: The correct answer is -
by coded instructions contained in DNA.
Explanation:
Protein synthesis is a two step process, which includes transcription ( conversion of DNA to mRNA) and translation (mRNA to protein).
DNA contains genetic information in the form of codons (sequence of three nucleotides that code for particular amino acid).
This information is transferred to mRNA through transcription, which is then followed by translation that produces particular protein through assembly of specific amino acid (brought by tRNA) according to codons present in the mRNA.
Thus, protein synthesis occurs due to coded instructions contained in the DNA.
