Textbook Question
Describe the structure of RNA polymerase in bacteria. What is the core enzyme? What is the role of the σ subunit?
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Ch. 13 - The Genetic Code and Transcription
Klug12th EditionConcepts of Genetics ISBN: 9780135564776
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Table of contents
- Ch. 1 - Introduction to Genetics17
- Ch. 2 - Mitosis and Meiosis36
- Ch. 3 - Mendelian Genetics51
- Ch. 4 - Extensions of Mendelian Genetics74
- Ch. 5 - Chromosome Mapping in Eukaryotes51
- Ch. 6 - Genetic Analysis and Mapping in Bacteria and Bacteriophages46
- Ch. 7 - Sex Determination and Sex Chromosomes33
- Ch. 8 - Chromosome Mutations: Variation in Number and Arrangement40
- Ch. 9 - Extranuclear Inheritance31
- Ch. 10 - DNA Structure and Analysis43
- Ch. 11 - DNA Replication and Recombination44
- Ch. 12 - DNA Organization in Chromosomes30
- Ch. 13 - The Genetic Code and Transcription54
- Ch. 14 - Translation and Proteins47
- Ch. 15 - Gene Mutation, DNA Repair, and Transposition41
- Ch. 16 - Regulation of Gene Expression in Bacteria29
- Ch. 17 - Transcriptional Regulation in Eukaryotes41
- Ch. 18 - Post-transcriptional Regulation in Eukaryotes33
- Ch. 19 - Epigenetics33
- Ch. 20 - Recombinant DNA Technology44
- Ch. 21 - Genomic Analysis36
- Ch. 22 - Applications of Genetic Engineering and Biotechnology36
- Ch. 23 - Developmental Genetics37
- Ch. 24 - Cancer Genetics34
- Ch. 25 - Quantitative Genetics and Multifactorial Traits54
- Ch. 26 - Population and Evolutionary Genetics45
Chapter 13, Problem 22
Present an overview of various forms of posttranscriptional RNA processing in eukaryotes. For each, provide an example.
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Understand that posttranscriptional RNA processing refers to the modifications that a primary RNA transcript undergoes to become a mature RNA molecule.
Identify the main types of posttranscriptional RNA processing in eukaryotes: 5' capping, 3' polyadenylation, splicing, RNA editing, and RNA transport.
5' capping: This involves the addition of a 7-methylguanylate cap to the 5' end of the RNA transcript. Example: The capping of mRNA in eukaryotic cells.
3' polyadenylation: This process adds a poly(A) tail to the 3' end of the RNA molecule. Example: The polyadenylation of mRNA, which aids in stability and export from the nucleus.
Splicing: This involves the removal of introns and joining of exons. Example: The splicing of pre-mRNA in eukaryotic cells to form mature mRNA.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Posttranscriptional RNA Processing
Posttranscriptional RNA processing refers to the modifications that RNA undergoes after transcription but before translation in eukaryotic cells. This includes several key processes that enhance the stability and functionality of RNA molecules, ensuring that they are properly prepared for protein synthesis.
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mRNA Processing
Capping and Polyadenylation
Capping involves the addition of a 7-methylguanylate cap to the 5' end of the RNA transcript, which protects the RNA from degradation and assists in ribosome binding during translation. Polyadenylation adds a poly(A) tail to the 3' end, which also stabilizes the RNA and facilitates its export from the nucleus.
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Splicing
Splicing is the process by which introns, or non-coding regions, are removed from the pre-mRNA transcript, and exons, or coding regions, are joined together. This process is crucial for generating mature mRNA that accurately reflects the coding sequence of the gene, allowing for the correct synthesis of proteins.
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Related Practice
Textbook Question
Write a paragraph describing the abbreviated chemical reactions that summarize RNA polymerase-directed transcription.
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Textbook Question
Messenger RNA molecules are very difficult to isolate in bacteria because they are rather quickly degraded in the cell. Can you suggest a reason why this occurs? Eukaryotic mRNAs are more stable and exist longer in the cell than do bacterial mRNAs. Is this an advantage or a disadvantage for a pancreatic cell making large quantities of insulin?
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Textbook Question
One form of posttranscriptional modification of most eukaryotic pre-mRNAs is the addition of a poly-A sequence at the 3' end. The absence of a poly-A sequence leads to rapid degradation of the transcript. Poly-A sequences of various lengths are also added to many bacterial RNA transcripts where, instead of promoting stability, they enhance degradation. In both cases, RNA secondary structures, stabilizing proteins, or degrading enzymes interact with poly-A sequences. Considering the activities of RNAs, what might be general functions of 3'-polyadenylation?
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Textbook Question
Describe the role of two forms of RNA editing that lead to changes in the size and sequence of pre-mRNAs. Briefly describe several examples of each form of editing, including their impact on respective protein products.
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Textbook Question
Substitution RNA editing is known to involve either C-to-U or A-to-I conversions. What common chemical event accounts for each?
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