Final answer:
The extent of complementarity of a miRNA with its target mRNA determines whether the mRNA will be immediately degraded or, instead, translationally repressed without immediate degradation. The role of miRNAs in post-transcriptional regulation includes immediate mRNA cleavage for fully complementary targets or repression for partial matches, thus influencing gene regulation.
Step-by-step explanation:
The extent of complementarity of a miRNA with its target mRNA determines whether the mRNA will be immediately degraded or whether the mRNA will first be transported elsewhere in the cell before degradation. MicroRNAs (miRNAs) are critical post-transcriptional regulators that target unwanted endogenous cellular RNAs for degradation or translational repression. They are transcribed from genes and processed in the cell.
An important aspect of their function involves a ribonucleoprotein complex known as the RNA-induced silencing complex (RISC). Mature miRNAs incorporated into RISC can bind to complementary sequences on mRNA molecules. When the miRNA is fully complementary to its target, it can lead to immediate cleavage and degradation of the mRNA. Partial complementarity, in contrast, may result in translational repression without immediate degradation.
RNA stability in the cytoplasm can be influenced by miRNAs by promoting decay, thus altering the amount of protein that is synthesized from the mRNA. This explains why miRNAs play a crucial role in gene regulation by affecting both the location and stability of their target mRNAs within the cell.