What occurs to the mRNA when RISC is activated?

When RISC (RNA-induced silencing complex) is activated, it plays a crucial role in gene regulation by targeting specific mRNA molecules. The primary function of RISC is to bind to these mRNAs that have complementary sequences to the small interfering RNA (siRNA) or microRNA (miRNA) that RISC carries. Once bound, RISC facilitates the degradation of the mRNA, leading to a reduction in the expression of the corresponding gene. This process is essential for post-transcriptional gene silencing, which is a critical mechanism in various biological processes, including development, cell differentiation, and response to stress.

The other choices do not align with RISC's function: replication does not occur because RISC does not synthesize RNA; translation is inhibited when RISC is engaged with mRNA; and storage of mRNA is also not a role of RISC, as its purpose is active regulation rather than preservation. Hence, degradation accurately describes the outcome of RISC activation in response to target mRNA.