Question at position 69 Which would result in mRNA degradation by siRNA/miRNA and RISC?many mismatchesa match with some mismatchesa perfect match单项选择题
A
many mismatches
B
a match with some mismatches
C
a perfect match

Question

Question at position 69 Which would result in mRNA degradation by siRNA/miRNA and RISC?many mismatchesa match with some mismatchesa perfect match

BlackTom AI · Accepted Answer

Starting with the question: we’re asked which situation would lead to mRNA degradation by siRNA/miRNA and the RISC complex.
Option 1: many mismatches. When an siRNA/miRNA is paired with an mRNA with many mismatches, binding is unstable and the silencing machinery is unlikely to efficiently recruit RISC for cleavage of the mRNA. In practice, miRNA often binds with imperfect complementarity to exert translational repression or destabilization, but extensive mismatches reduce effective slicing of the mRNA. Therefore, this option is unlikely to cause robust mRNA degradation via RISC.
Option 2: a match with some mismatches. Partial complementarity can sometimes trigger translational repression or lead to less efficient degradation, depending on the organism and exact pairing. However, because there are mismatches, the canonical slicer activity of RISC is not strongly engaged in the same way as with near-perfect pairing, so degradation is not as reliable or efficient as with a perfect match. This makes degradation via slicer activity less certain.
Option 3: a perfect match. A perfect or near-perfect base-pairing between the guide siRNA/miRNA and the target mRNA strongly positions the Argonaute slicer within RISC to cleave the mRNA, resulting in effective degradation. This is the classic mechanism of siRNA-mediated cleavage, and is the scenario most associated with direct mRNA degradation by RISC.
To compare the implications: many mismatches undermine efficient cleavage; some mismatches allow repression without robust slicing; a perfect match promotes direct cleavage and degradation. The correct mechanism relies on the level of complementarity guiding the RISC’s endonucleolytic activity, with perfect pairing aligning with mRNA slicing and rapid degradation, whereas imperfect pairing tends toward repression without cleavage or reduced targeting efficiency.
In summary, the options reflect a spectrum of complementarity effects on RISC: extreme mismatch reduces degradation likelihood, partial mismatch reduces efficiency, and perfect matching optimally enables RISC-mediated cleavage and degradation of the target mRNA.

Question at position 69 Which would result in mRNA degradation by siRNA/miRNA and RISC?many mismatchesa match with some mismatchesa perfect match单项选择题

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