What is the primary function of transcription factors?

Transcription factors play a crucial role in the regulation of gene expression by binding to specific DNA sequences near genes. Their primary function is to facilitate or inhibit the transcription of these genes into messenger RNA (mRNA), which is the first step in the process of gene expression. By binding to promoters and enhancers, transcription factors can recruit or block the action of RNA polymerase, the enzyme responsible for synthesizing RNA from a DNA template. This regulation can determine whether a gene is turned on or off, influencing the amount of protein produced in a cell, which ultimately affects cell function and behavior.

In contrast, the other options do not accurately describe the primary role of transcription factors. Modifying RNA after transcription pertains to post-transcriptional modifications such as splicing, capping, and polyadenylation, which are not the domain of transcription factors. Replicating DNA involves the action of DNA polymerases and other enzymes during the process of DNA replication, particularly during cell division, rather than transcription factors. Destroying malfunctioning proteins is the responsibility of cellular machinery such as proteasomes and lysosomes, focusing on protein degradation rather than gene expression control.