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Ch. 13 - The Genetic Code and Transcription
Klug - Concepts of Genetics 12th Edition
Klug12th EditionConcepts of Genetics ISBN: 9780135564776Not the one you use?Change textbook
All textbooksKlug 12th EditionCh. 13 - The Genetic Code and TranscriptionProblem 33a
Chapter 13, Problem 33a

Isoginkgetin is a cell-permeable chemical isolated from the Ginkgo biloba tree that binds to and inhibits snRNPs.
What types of problems would you anticipate in cells treated with isoginkgetin?

Verified step by step guidance
1
Understand the role of snRNPs (small nuclear ribonucleoproteins) in the cell. These are essential components of the spliceosome, which is responsible for removing introns from pre-mRNA during the process of RNA splicing.
Recognize that inhibiting snRNPs would disrupt the splicing process. This means that pre-mRNA would not be properly processed into mature mRNA, leading to the retention of introns in the RNA transcripts.
Consider the downstream effects of improperly spliced mRNA. Such mRNA may be degraded by the cell's quality control mechanisms, or if translated, it could produce nonfunctional or harmful proteins.
Think about the broader cellular consequences. A lack of functional proteins due to defective mRNA processing could impair essential cellular processes, potentially leading to cell death or dysfunction.
Relate this to the specific context of the problem. Cells treated with isoginkgetin would likely exhibit issues such as reduced protein synthesis, accumulation of unprocessed RNA, and possibly activation of stress or apoptotic pathways due to the disruption of normal gene expression.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

snRNPs (small nuclear ribonucleoproteins)

snRNPs are essential components of the spliceosome, a complex responsible for the splicing of pre-mRNA in eukaryotic cells. They play a critical role in removing introns and joining exons, which is vital for producing mature mRNA. Inhibition of snRNPs can lead to improper splicing, resulting in dysfunctional proteins and potentially causing various cellular malfunctions.
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mRNA Processing

mRNA splicing

mRNA splicing is the process by which introns are removed from pre-mRNA transcripts and exons are joined together to form mature mRNA. This process is crucial for gene expression, as it determines which protein variants are produced. Disruption of splicing due to isoginkgetin could lead to the production of nonfunctional or harmful proteins, affecting cell viability and function.
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mRNA Processing

cellular stress responses

Cellular stress responses are mechanisms that cells activate in response to various stressors, including chemical inhibitors like isoginkgetin. These responses can include apoptosis (programmed cell death), activation of stress-related signaling pathways, and changes in gene expression. If snRNPs are inhibited, cells may experience increased stress, leading to potential cell death or dysfunction due to the accumulation of improperly processed mRNA.
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Translesion Synthesis
Related Practice
Textbook Question

M. Klemke et al. (2001) discovered an interesting coding phenomenon in which an exon within a neurologic hormone receptor gene in mammals appears to produce two different protein entities (and ALEX). The following is the DNA sequence of the exon's end derived from a rat.

 5'-gtcccaaccatgcccaccgatcttccgcctgcttctgaagATGCGGGCCCAG

The lowercase letters represent the initial coding portion for the protein, and the uppercase letters indicate the portion where the ALEX entity is initiated. (For simplicity, and to correspond with the RNA coding dictionary, it is customary to represent the coding (non-template) strand of the DNA segment.)

Provide the amino acid sequence for each coding sequence. In the region of overlap, are the two amino acid sequences the same?

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Textbook Question

M. Klemke et al. (2001) discovered an interesting coding phenomenon in which an exon within a neurologic hormone receptor gene in mammals appears to produce two different protein entities (and ALEX). The following is the DNA sequence of the exon's end derived from a rat.

 5'-gtcccaaccatgcccaccgatcttccgcctgcttctgaagATGCGGGCCCAG

The lowercase letters represent the initial coding portion for the protein, and the uppercase letters indicate the portion where the ALEX entity is initiated. (For simplicity, and to correspond with the RNA coding dictionary, it is customary to represent the coding (non-template) strand of the DNA segment.)

Are there any evolutionary advantages to having the same DNA sequence code for two protein products? Are there any disadvantages?

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Textbook Question

Recent observations indicate that alternative splicing is a common way for eukaryotes to expand their repertoire of gene functions. Studies indicate that approximately 50 percent of human genes exhibit alternative splicing and approximately 15 percent of disease-causing mutations involve aberrant alternative splicing. Different tissues show remarkably different frequencies of alternative splicing, with the brain accounting for approximately 18 percent of such events [Xu et al. (2002). Nucl. Acids Res. 30:3754–3766].

Why might some tissues engage in more alternative splicing than others?

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Textbook Question

Isoginkgetin is a cell-permeable chemical isolated from the Ginkgo biloba tree that binds to and inhibits snRNPs.

Would this be most problematic for E. coli cells, yeast cells, or human cells? Why?

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