Question 1

Which of the following does not take part in the degradation process of eukaryotic mRNAs?

Accepted Answer

Capping, a process that adds a modified guanine nucleotide to the 5' end of mRNA, is a protective mechanism that prevents degradation. Therefore, it does not take part in the degradation process of eukaryotic mRNAs. Endonucleolytic cleavage, exonucleolytic decay, and poly(A) shortening, on the other hand, are all involved in the degradation process of eukaryotic mRNAs.

Question 2

Cells use several ways to avoid the translation of improperly processed mRNA molecules._____ is(are)considered mRNA surveillance mechanisms.

Accepted Answer

All three options listed (nonsense-mediated decay, non-stop decay, and no-go decay) are considered mRNA surveillance mechanisms used by cells to avoid the translation of improperly processed mRNA molecules.

Question 3

Knocking out the dicer gene in mammals would lead to a loss of:

Accepted Answer

The dicer gene is essential for the processing of miRNAs, which are small non-coding RNAs that play a crucial role in post-transcriptional gene regulation. Therefore, knocking out the dicer gene would lead to a loss of miRNAs.

Question 4

Which type of RNA participates in nuclear export of mRNA?

Accepted Answer

hnRNA (heterogeneous nuclear RNA) participates in nuclear export of mRNA. After transcription in the nucleus, pre-mRNA undergoes extensive processing, including capping, splicing, and polyadenylation. The processed mRNA then leaves the nucleus through nuclear pores with the help of hnRNPs.

Question 5

The RISC complex contains which one of the following proteins?

Accepted Answer

The RISC complex (RNA-induced silencing complex) includes small RNA molecules such as microRNAs, as well as a member of the Argonaute family of proteins, which interacts with the microRNA to target specific mRNAs for degradation or translational repression. DGCR8, Dicer, and Drosha are all involved in the processing of microRNA precursors, but are not part of the RISC complex itself.

Question 6

The mammalian target of rapamycin (mTOR)complex 1 plays an integral role in all but one of these processes.Which one is mTOR not directly involved in?

Accepted Answer

mTOR complex 1 is primarily involved in promoting cell growth, ribosome biogenesis, and Pol III transcription, but it is not directly involved in protein degradation.

Question 7

How is the 5´ cap added to nascent RNAs?

Accepted Answer

The answer of How is the 5´ cap added to...

Question 8

Transport of unspliced HIV mRNA from the nucleus to the cytoplasm of host cells is promoted by a virus-encoded protein named

Accepted Answer

Rev is the virus-encoded protein that promotes the transport of unspliced HIV mRNA from the nucleus to the cytoplasm of host cells.

Question 9

The 45S pre-rRNA molecule

Accepted Answer

A) The 45S pre-rRNA molecule is a key component of the nucleolus, which is responsible for ribosome biogenesis. Therefore, the molecule can organize a nucleolus when present in a single copy.
B) The 45S pre-rRNA molecule is encoded by tandemly arranged genes, which are clustered in a genomic region called the nucleolar organizer region (NOR). In human cells, this region is located on the short arms of five acrocentric chromosomes (chromosomes 13, 14, 15, 21, and 22).
C) The 45S pre-rRNA molecule contains specific methylated bases, such as 2'-O-methylated nucleotides, which are important for ribosome function. Therefore, the molecule is methylated on specific bases.

Question 10

A ribozyme is an RNA sequence

Accepted Answer

Ribozymes are RNA molecules that have the ability to catalyze specific biochemical reactions, similar to the action of protein enzymes. They often require Mg²⁺ ions as cofactors for their catalytic activity, can cleave RNA molecules in a sequence-specific manner, and are integral components of the spliceosome, where they play a crucial role in the splicing of pre-mRNA.

Question 11

The cell contains numerous organelles,all with specific functions,but the one that plays a key role in the digestion of ribosomes,mitochondria,and other organelles is the:

Accepted Answer

Autophagosomes are responsible for the degradation and recycling of cellular components, including ribosomes, mitochondria, and other organelles through a process called autophagy. Endosomes are responsible for the sorting and processing of proteins and lipids, nucleosomes are structures that package DNA, and proteasomes are responsible for the degradation of proteins that are targeted for destruction.

Question 12

Which of these events does not occur within the nucleus?

Accepted Answer

RNA editing in protozoans typically occurs in the mitochondria, not in the nucleus.

Question 13

Which of the following regarding the P-body is FALSE?

Accepted Answer

P-body is not the site where polysomes form. Polysomes are formed in active regions of the cytoplasm where ribosomes bind to mRNA and start synthesizing proteins. P-bodies are sites for mRNA degradation and storage.

Question 14

What are hnRNP proteins? How were they identified?

Accepted Answer

The answer of What are hnRNP proteins? How were they...

Question 15

In animal cells,nearly all cytoplasmic mRNAs have a 3´ poly(A)tail,which is added to the pre-mRNA before splicing.What proteins are involved in polyadenylation? Indicate their order of association with pre-mRNA and their functions.

Accepted Answer

The answer of In animal cells,nearly all cytoplasmic mRNAs have...

Question 16

snRNP-dependent splicing of pre-mRNA is thought to have evolved from the self-splicing properties inherent in the sequence of either group I or II introns.Alternative splicing of pre-mRNAs processed by spliceosomes has been demonstrated,whereas this phenomenon does not occur in RNA transcripts that undergo self-splicing.Explain this difference.

Accepted Answer

The answer of snRNP-dependent splicing of pre-mRNA is thought to...

Question 17

Synthesis of pre-rRNA occurs in the

Accepted Answer

Pre-rRNA synthesis occurs in the nucleolus, a specialized substructure within the nucleus of eukaryotic cells. The nucleolus is responsible for the production and assembly of ribosomes, which are essential for protein synthesis.

Question 18

Which of the following are NOT found within the nucleus?

Accepted Answer

P-bodies are cytoplasmic structures that contain mRNA and protein, and they are important for regulating mRNA degradation and translational repression. Cajal bodies, histone locus bodies, and nucleoli are all substructures found within the nucleus.

Question 19

microRNAs play a key role in which of the following?

Accepted Answer

The answer of microRNAs play a key role in which...

Question 20

You are using a variety of techniques to study how the RISC complex differs between siRNAs and miRNAs and have found that what distinguishes an RISC complex containing an siRNA from one containing an miRNA is that:

Accepted Answer

The siRNA base-pairs perfectly with its target mRNA, leading to cleavage of the mRNA and inhibition of translation. In contrast, miRNAs base-pair imperfectly with their target mRNAs and primarily inhibit translation.

Quiz 9: Post-Transcriptional Gene Control