Which molecule specifies the amino acid sequence of protein products?

The molecule that specifies the amino acid sequence of protein products is mRNA, or messenger RNA. During the process of transcription, DNA is copied to produce mRNA, which serves as a template for translating the genetic code into a sequence of amino acids. Each three-nucleotide sequence, or codon, on the mRNA corresponds to a specific amino acid.

In the translation process that occurs in the ribosome, the mRNA strand is read by ribosomal RNA (rRNA), and transfer RNA (tRNA) molecules bring the appropriate amino acids to the growing polypeptide chain according to the instructions provided by the codons on the mRNA. While DNA contains the original genetic information, it is the mRNA that directly specifies the sequence of amino acids that will form the final protein product. This key role of mRNA in conveying information from DNA to the protein synthesis machinery of the cell makes it essential for producing proteins.