Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

12. Gene Regulation in Prokaryotes

Tryptophan Operon and Attenuation

Genetics

12. Gene Regulation in Prokaryotes

Tryptophan Operon and Attenuation

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2:21 minutes

Problem 6

Textbook Question

Is attenuation the product of an allosteric effect? Is attenuation the result of a transcriptional or a translational activity? Explain your answers.

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Attenuation is a regulatory mechanism in prokaryotic gene expression, particularly in operons like the trp operon in bacteria.

It involves the premature termination of transcription, which is influenced by the formation of specific secondary structures in the mRNA.

Attenuation is not the product of an allosteric effect. Allosteric effects involve the binding of a molecule at a site other than the active site on a protein, often affecting enzyme activity.

Attenuation is primarily a transcriptional activity because it regulates the continuation of RNA polymerase along the DNA, affecting the transcription process.

In summary, attenuation is a transcriptional regulatory mechanism, not an allosteric effect, as it involves the formation of mRNA structures that influence transcription termination.

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Key Concepts

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

Attenuation

Attenuation is a regulatory mechanism in gene expression, particularly in prokaryotes, where the transcription of a gene is prematurely terminated. This process is influenced by the formation of specific RNA structures during transcription, which can be affected by the availability of certain metabolites. It serves as a way for cells to conserve resources by halting the production of proteins when they are not needed.

Allosteric Effect

An allosteric effect refers to the regulation of a protein's function through the binding of a molecule at a site other than the active site, leading to a conformational change. This can enhance or inhibit the protein's activity, impacting processes such as enzyme function or receptor signaling. In the context of attenuation, allosteric effects can influence the formation of RNA structures that determine whether transcription continues or stops.

Transcriptional vs. Translational Regulation

Transcriptional regulation involves controlling the synthesis of RNA from DNA, determining which genes are expressed and to what extent. In contrast, translational regulation pertains to the control of protein synthesis from mRNA. Attenuation primarily acts at the transcriptional level by affecting the continuation of RNA synthesis, although it can also have implications for translation depending on the RNA structures formed.

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Transcriptional regulation of operon gene expression involves the interaction of molecules with one another and of regulatory molecules with segments of DNA. In this context, define and give an example of each of the following:

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Identify similarities and differences between an inducible operon and a repressible operon in terms of

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Identify similarities and differences between an inducible operon and a repressible operon in terms of

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The trpL region contains four repeated DNA sequences that lead to the formation of stem-loop structures in mRNA. What are these stem-loop structures, and how do they affect transcription of the structural genes of the trp operon?

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Explain the circumstances under which attenuation of operon gene expression is advantageous to a bacterial organism. Would you expect attenuation to be found in a single-celled eukaryote? In a multicelled eukaryote?

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Describe the role of attenuation in the regulation of tryptophan biosynthesis.

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Textbook Question

Attenuation of the trp operon was viewed as a relatively inefficient way to achieve genetic regulation when it was first discovered in the 1970s. Since then, however, attenuation has been found to be a relatively common regulatory strategy. Assuming that attenuation is a relatively inefficient way to achieve genetic regulation, what might explain its widespread occurrence?

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