What is the main function of mRNA molecules in gene expression?

The main function of mRNA molecules in gene expression is to carry genetic information from the nucleus to the ribosomes, where proteins are synthesized. This process begins with transcription, where DNA is transcribed into mRNA in the nucleus. Once synthesized, mRNA travels out of the nucleus and into the cytoplasm, acting as a template that conveys the specific sequence of nucleotides that correspond to the order of amino acids in a protein.

At the ribosomes, this coded information directs the synthesis of proteins through the process of translation, during which tRNA molecules bring the appropriate amino acids, and ribosomes facilitate the assembly of these amino acids into polypeptides, ultimately forming functional proteins. This central role of mRNA in mediating the flow of genetic information is critical for the proper expression of genes and the functioning of cells.

Other options relate to different roles in gene expression and protein synthesis, but they do not accurately describe the primary function of mRNA.