What is the primary function of mRNA?

The primary function of mRNA, or messenger RNA, is to serve as a template for protein synthesis. This process begins when a specific segment of DNA is transcribed into mRNA during the transcription phase of gene expression. Once synthesized, the mRNA molecule carries the genetic information from the DNA in the nucleus to the ribosome, the site of protein synthesis in the cell.

At the ribosome, the sequence of nucleotides in the mRNA is translated into a specific sequence of amino acids, which are the building blocks of proteins. This process involves the ribosome reading the mRNA in sets of three nucleotides, called codons, with each codon corresponding to a specific amino acid. Through this mechanism, mRNA effectively conveys the genetic instructions that determine the structure and function of proteins in the cell, making it an essential component of the central dogma of molecular biology, which outlines the flow of genetic information.

In contrast, the other options refer to different processes or components in cellular biology—it does not replicate DNA, transcribe RNA directly from DNA, nor provide structural support to DNA, which are functions associated with other molecules or processes in the cell.