In Many Animals, SiRNAs Can Only Function Within the Cell

question 37

Multiple Choice

In many animals, siRNAs can only function within the cell in which the siRNA is introduced. In contrast, the worm Caenorhabditis elegans can be fed with bacteria that synthesize double-stranded RNAs, and the RNAi spreads throughout the animal. A genetic screen to identify genes involved in systemic RNAi led to the discovery of Sid-1, a transmembrane protein expressed in most tissues in the adult worm. Loss-of-function mutations in the gene encoding Sid-1 restrict the RNAi activity to the cells surrounding the digestive tract after siRNA feeding. Ectopic expression of Sid-1 in Drosophila melanogaster cells that normally lack systemic RNAi and are unable to take up siRNAs from the medium, enables these cells to passively take up siRNA . These findings suggest that …

• A) Sid-1 is necessary and sufficient for systemic RNAi and siRNA uptake, respectively.
• B) Sid-1 is necessary but not sufficient for systemic RNAi and siRNA uptake, respectively.
• C) Sid-1 is not necessary but is sufficient for systemic RNAi and siRNA uptake, respectively.
• D) Sid-1 is not necessary and not sufficient for systemic RNAi and siRNA uptake, respectively.

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Definitions:

Defamation

A false communication that injures someone's reputation, either through written statements (libel) or spoken statements (slander).

Negligence Per Se

A doctrine that allows a judge or jury to infer duty and breach of duty from the fact that a defendant violated a criminal statute that was designed to prevent the type of harm that the plaintiff incurred.

Modified Comparative Negligence

A defense accepted in some states whereby the defendant is not liable for the percentage of harm that he or she can prove is due to the plaintiff’s own negligence if the plaintiff’s negligence is responsible for less than 50 percent of the harm; if the defendant establishes that the plaintiff’s negligence caused more than 50 percent of the harm, the defendant has no liability.

Intentional Interference

Deliberate actions taken to disrupt or harm another party's contractual or business relationships.