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

Lac Operon

Genetics

12. Gene Regulation in Prokaryotes

Lac Operon

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1:40 minutes

Problem 2b

Textbook Question

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:
Repressor

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Understand the concept of a repressor: A repressor is a regulatory protein that binds to specific DNA sequences, typically at the operator region of an operon, to inhibit transcription. This prevents RNA polymerase from transcribing the downstream genes.

Explain the mechanism of action: The repressor protein binds to the operator region of the operon. This binding physically blocks RNA polymerase from moving along the DNA, thereby preventing the transcription of the operon's genes.

Provide an example: In the lac operon of *E. coli*, the lac repressor protein binds to the operator region in the absence of lactose. This prevents the transcription of genes responsible for lactose metabolism.

Discuss the role of an inducer: In the lac operon example, when lactose (or its isomer allolactose) is present, it binds to the repressor protein. This causes a conformational change in the repressor, preventing it from binding to the operator and allowing transcription to proceed.

Summarize the importance: Repressors are crucial for regulating gene expression, ensuring that genes are only expressed when needed, which conserves cellular resources and allows for efficient adaptation to environmental changes.

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Key Concepts

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

Repressor

A repressor is a type of regulatory protein that binds to specific DNA sequences, inhibiting the transcription of genes. By blocking RNA polymerase from accessing the promoter region, repressors prevent gene expression. An example is the lac repressor in the lac operon of E. coli, which binds to the operator region in the absence of lactose, preventing the transcription of genes involved in lactose metabolism.

Operon

An operon is a cluster of genes under the control of a single promoter, allowing coordinated regulation of gene expression. Operons are common in prokaryotes and enable the efficient use of resources by expressing genes only when needed. The lac operon, for instance, contains genes that encode proteins for lactose utilization, which are expressed only when lactose is present and glucose is scarce.

Transcriptional Regulation

Transcriptional regulation refers to the mechanisms that control the rate of gene transcription, determining how much of a gene's product is made. This regulation can involve various factors, including repressors, activators, and the availability of transcription factors. It is crucial for cellular responses to environmental changes, allowing organisms to adapt by turning genes on or off as needed.

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Textbook Question

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:

Allostery

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