Final answer:
The enzyme that cuts double-stranded RNA (dsRNA) is called DICER, which works in conjunction with the RNA-induced silencing complex (RISC) to degrade matching messenger RNAs and protect the cell from viral infections.
Step-by-step explanation:
The enzyme that chops up double-stranded RNA (dsRNA) is called DICER. DICER is responsible for cutting dsRNA into shorter fragments in a process that defends the cell against viral infections. Once DICER cuts the dsRNA, one strand of the resultant fragment is incorporated into the RNA-induced silencing complex (RISC). The RISC then uses this strand to look for and degrade messenger RNA (mRNA) sequences that match the dsRNA fragment, thereby preventing the virus from hijacking the cell's machinery to reproduce its own proteins.