In the transcription process, the ribonucleic acid (RNA) polymerase enzyme attaches itself to the deoxyribonucleic acid (DNA) molecule and starts its transcription process. During this process, one strand acts as the template strand from which mRNA would be synthesized by the enzyme. The strand that is opposite to the template strand would be similar to the sequences developed in the transcribed mRNA molecule.
Since it is the sequence that is transcribed in the mRNA that ends up as the protein molecule, the sequence is highly essential in making sure that the correct protein is being synthesized by a gene. Any change in the sequence would lead to the synthesis of a completely different protein.