What is the process by which DNA directs protein synthesis?

The process by which DNA directs protein synthesis is known as gene expression. Gene expression encompasses the transcription of DNA into messenger RNA (mRNA) and the subsequent translation of mRNA into a polypeptide chain, which ultimately folds into a functional protein. This process is crucial because it allows the genetic information encoded in DNA to be translated into the proteins that perform a vast array of functions within cells.

During transcription, an enzyme called RNA polymerase binds to a specific region of the DNA and synthesizes the mRNA strand complementary to the DNA template. Following transcription, the mRNA undergoes processing before it is translated into a protein. In translation, ribosomes read the mRNA sequence in sets of three nucleotides (codons) and assemble amino acids in the correct order to build the protein, guided by the sequence of codons.

Other options such as DNA replication refer specifically to the process by which DNA is copied before cell division, while cellular respiration is the process by which cells convert glucose and oxygen into energy, and photosynthesis pertains to the conversion of light energy into chemical energy by plants. These processes are essential for life but do not directly involve the mechanism through which DNA influences protein synthesis.