Double Stranded Rna

=Describe two cellular processes that involve a covalent linkage between DNA and a protein.

Answers: One method is called Strand Exchange mechanism where one of the single-strand 3ʹ ends from the damaged DNA molecule emerges its way into the template duplex and searches it for homologous sequences through base-pairing. Once the base pairing is established, DNA polymerase extends the invading strand by using the information provided by the undamaged template molecule, thus restoring the damaged DNA. This mechanism is achieved by interaction of a protein called Rad51 found in eukaryotes. In bacterium, the protein that utilizes the strand exchange is achieved by RecA protein. In order to catalyze strand exchange, RecA protein first binds to the single

Answer: Because double stranded RNA can induce silencing of the gene based on the base pairing principles. For example, presence of double stranded RNA triggers RNA interference by attracting the protein complex called Dicers, a nuclease which produces miRNAs. The dicer nuclease cleaves double stranded RNA into small fragments which is about 23 nucleotides, these fragments are called small interfering RNAs. These SiRNAs are coupled with Argonaute and other components of RISC protein which directs to pair with complementary RNA molecule which leads to the destruction of the targeted mRNA. The big picture here is that, the reason one of the strand is discarded due to the intended manipulation of the gene expression in order to stop or silence that particular gene. The cycle of destruction doesn’t end here, once the RISC protein is released, it couple with the discarded RNA strand from the primary breaking of the double stranded RNA from the beginning and it can attack other complimentary RNA molecules and continue the intended gene silencing process. (Lecture 11 slides from 11/20)