Question 1

Proteins that prevent translation of mRNA are called .&#10;A)nucleases&#10;B)translational repressors&#10;C)proteases&#10;D)mRNA silencers

Accepted Answer

Translational repressors are proteins that prevent the translation of mRNA by binding to specific sequences on the mRNA molecule, thereby blocking the ribosome from initiating translation. Nucleases and proteases are enzymes that degrade nucleic acids and proteins, respectively. mRNA silencers are a similar concept to translational repressors but are not a commonly used term in biology.

Question 2

Which statement is false?&#10;A)Nucleases are not part of the RNAi scenario.&#10;B)Some small RNAs help stabilize the mRNA and protect it from degradation.&#10;C)RNAi is a form of gene silencing that involves degradation of target RNAs.&#10;D)Riboswitches bind small molecules.

Accepted Answer

Nucleases are actually important players in the RNAi pathway, as they are responsible for cleaving the targeted RNAs into smaller fragments.

Question 3

RISC proteins recognize small RNA fragments called .&#10;A)Slicer&#10;B)Dicer&#10;C)siRNA&#10;D)miRNA

Accepted Answer

siRNA are small RNA fragments that are recognized by RISC proteins.

Question 4

RNA interference is triggered by .&#10;A)dsDNA&#10;B)dsRNA&#10;C)ssDNA&#10;D)ssRNA

Accepted Answer

RNA interference is triggered by double-stranded RNA (dsRNA), which is processed by the enzyme Dicer into small interfering RNAs (siRNAs) that can then bind to and degrade homologous mRNA molecules, leading to post-transcriptional gene silencing. dsDNA and ssDNA do not trigger RNA interference, and ssRNA is not a common trigger for this process, although some RNA viruses can produce dsRNA intermediates during their replication cycle, which can then elicit RNA interference in infected cells.

Question 5

Attenuation of RNA involves the formation of alternate stem-loop structures.

Accepted Answer

Attenuation of RNA involves the formation of alternate stem-loop structures. During transcription, the nascent RNA strand folds back on itself to form a hairpin loop. Depending on the sequence and length of the loop, it can either terminate transcription or allow it to continue. This process is known as attenuation and is commonly found in bacterial gene regulation.

Question 6

RNA interference occurs in bacteria.

Accepted Answer

RNA interference is a biological process found in eukaryotic organisms, including animals, plants, and fungi, but it is not a mechanism observed in bacteria.

Question 7

The blocking of translation of an mRNA by miRNA occurs because the miRNA .&#10;A)binds to the 3'-UTR of the mRNA and prevents translation&#10;B)targets the mRNA for degradation by Slicer&#10;C)binds to the 5'-UTR to prevent the ribosome from binding&#10;D)folds into alternative stem-loop structure and protects the mRNA from nuclease cleavage

Accepted Answer

miRNA binds to the 3'-UTR of the mRNA and forms an RNA-induced silencing complex (RISC) that prevents translation. This occurs through a combination of blocking ribosome binding and promoting deadenylation of the mRNA, which ultimately leads to degradation by exonucleases.

Question 8

In bacteria,the system destroys incoming viral DNA and RNA.&#10;A)RISC&#10;B)Dicer&#10;C)Slicer&#10;D)CRISPR

Accepted Answer

The CRISPR (Clustered Regularly Interspaced Short Palindromic Repeats) system in bacteria functions as an adaptive immune system, in which it can recognize and destroy viral DNA/RNA that has previously infected the bacteria. The CRISPR system involves several proteins, including Cas9, that can specifically target and cut viral DNA/RNA molecules. Therefore, the CRISPR system is the best choice for the given scenario.

Question 9

Riboswitches .&#10;A)can bind small molecules&#10;B)are useful in translational control&#10;C)are found on the 5' end of the mRNA&#10;D)are all of the above

Accepted Answer

Riboswitches are RNA molecules that can bind small molecules, allowing them to regulate gene expression. They are often found on the 5' end of mRNA and play a key role in translational control. Therefore, choice D is the correct answer.

Question 10

Which nuclease is responsible for generating siRNA?&#10;A)Ribonuclease P&#10;B)Dicer&#10;C)Slicer&#10;D)RISC

Accepted Answer

Dicer is responsible for generating siRNA by cleaving double-stranded RNA into small fragments.

Deck 18: Regulation at the RNA Level