What is the primary action triggered by small interfering RNA (siRNA)?

The primary action triggered by small interfering RNA (siRNA) is to trigger the degradation of other RNA molecules. siRNA is a class of double-stranded RNA that plays a crucial role in the RNA interference (RNAi) pathway. When siRNA is incorporated into a protein complex known as the RNA-induced silencing complex (RISC), it guides the complex to complementary mRNA strands. This binding leads to the cleavage of the target mRNA, which results in its degradation and prevents it from being translated into proteins.

This mechanism is a key regulatory process in gene expression because it allows cells to silence specific genes and regulate the levels of proteins produced within the cell. By degrading mRNA, siRNA effectively decreases the availability of the corresponding messages, thereby influencing the expression of genes in a highly precise manner.

The other options do not accurately describe the main role of siRNA. For instance, while modulation of translation efficiency could be a secondary effect of siRNA activity, the primary action is the degradation of RNA. Additionally, siRNA does not initiate transcription processes or transport DNA segments. Thus, the focus on degradation underlines the core function of siRNA in gene silencing.