Q: A gene has 12 possible exons for exon 4, 48 for exon 6, 33 for exon 9, and 2 for exon 17. How many different polypeptides can be produced through alternative splicing of this gene?

$$12 \times 48 \times 33 \times 2 = 38,016$$

Question 1

Which type of alternative splicing is most prevalent in animals and accounts for nearly 40% of alternative splicing events?

Accepted Answer

Cassette exons

Question 2

A gene has 12 possible exons for exon 4, 48 for exon 6, 33 for exon 9, and 2 for exon 17. How many different polypeptides can be produced through alternative splicing of this gene?

Accepted Answer

$$12 	imes 48 	imes 33 	imes 2 = 38,016$$

Question 3

Which mechanism allows for the swapping of protein domains encoded by different exons, such that inclusion of one exon leads to exclusion of others in the same cluster?

Accepted Answer

Mutually exclusive exons

Question 4

What is the primary function of SR proteins in the regulation of alternative splicing?

Accepted Answer

They recruit spliceosome components by binding to splicing enhancers.

Question 5

In Drosophila, what is the consequence of SXL protein presence during embryonic development?

Accepted Answer

It initiates female-specific splicing events, leading to female differentiation.

Question 6

Which genetic disorder is caused by CTG repeat expansion leading to splicing abnormalities and widespread alternative splicing defects in muscle cells and neurons?

Accepted Answer

Myotonic dystrophy

Question 7

What is the median half-life ($$t_{1/2}) of $$mRNA in humans?

Accepted Answer

$$7.1$$ hours

Question 8

Which pathway involves exoribonuclease enzymes shortening the poly-A tail, leading to mRNA degradation?

Accepted Answer

Deadenylation-dependent decay

Question 9

What is the role of cytoplasmic polyadenylation element binding protein (CPEB) in mRNA regulation?

Accepted Answer

It binds to the cytoplasmic polyadenylation element and regulates poly-A tail length.

Question 10

Which enzyme catalyzes the addition of a phosphate group to serine, tyrosine, or threonine residues in proteins?

Accepted Answer

Kinase

Question 11

What is the function of the proteasome in posttranslational regulation?

Accepted Answer

It degrades proteins that have been tagged with a ubiquitin molecule.

Question 12

Which type of small noncoding RNA arises in response to virus infection or expression of transposons and triggers degradation of the source RNA?

Accepted Answer

siRNA

Question 13

What is the main difference between siRNA and miRNA in their mechanism of action?

Accepted Answer

miRNA targets mRNA from a different gene, while siRNA targets its own source mRNA.

Question 14

Which of the following would be most efficient at changing gene expression through RNA interference (RNAi)?

Accepted Answer

Double-stranded RNA (dsRNA) that includes the gene sequence you wish to silence

Question 15

In Duchenne muscular dystrophy, what is the effect of introducing linc-MD1 into cultured myoblasts from DMD patients?

Accepted Answer

It partially restores muscle cell differentiation.

Question 16

Which mechanism of mRNA localization involves the cytoskeletal network and motor proteins for direct transport?

Accepted Answer

Direct transport

Question 17

What is the effect of phosphorylation on protein function?

Accepted Answer

It usually induces conformational and functional changes in proteins.

Question 18

Which posttranscriptional regulatory mechanism is most likely to be involved in the rapid response to environmental signals in eukaryotic cells?

Accepted Answer

Posttranscriptional regulation

Question 19

What is the role of Argonaute protein in the RNA-induced silencing complex (RISC)?

Accepted Answer

It is an endoribonuclease that cleaves mRNA in the region of siRNA–mRNA complementarity.

Question 20

Which of the following best explains why the proteome is larger than the number of protein-coding genes in humans?

Accepted Answer

Alternative splicing generates multiple protein isoforms from a single gene.

Posttranscriptional Regulation in Eukaryotes: Mechanisms and Implications

Study Guide - Practice Questions

Study Guide - Flashcards