What is the primary function of RNA polymerase in gene expression?

The primary function of RNA polymerase in gene expression is transcribing DNA into RNA. During the process of transcription, RNA polymerase binds to a specific section of the DNA at the promoter region of a gene. It unwinds the DNA double helix and synthesizes a complementary strand of RNA by incorporating ribonucleotides that pair with the DNA template strand. This RNA strand will ultimately serve as mRNA, which carries the genetic information from the DNA to the ribosomes for protein synthesis.

The process of transcribing DNA into RNA is crucial because it is the first step in gene expression, allowing the information encoded in the DNA to be expressed in the form of proteins. Without RNA polymerase, the transcription process would not occur, and the gene could not be expressed.