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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Multiple Choice

Which of the following conditions will result in maximal expression of the lac operon in E. coli?

Lactose present, glucose absent

Lactose present, glucose present

Lactose absent, glucose absent

Lactose absent, glucose present

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Verified step by step guidance

Understand the role of the lac operon: It is a set of genes in E. coli that are involved in the metabolism of lactose. The operon is regulated to be expressed only when lactose is available and glucose is scarce, ensuring efficient energy use.

Recall that the lac operon is controlled by two main factors: the presence of lactose and the presence of glucose. Lactose acts as an inducer by binding to the repressor and preventing it from blocking transcription, while glucose presence affects the levels of cyclic AMP (cAMP), which influences the activity of the catabolite activator protein (CAP).

Analyze the effect of lactose presence: When lactose is present, it binds to the lac repressor, causing it to release from the operator region, allowing transcription of the lac genes to proceed.

Analyze the effect of glucose absence: When glucose is absent, the concentration of cAMP increases. cAMP binds to CAP, and this complex binds to the promoter region, enhancing RNA polymerase binding and increasing transcription of the lac operon.

Combine these effects: Maximal expression of the lac operon occurs when lactose is present (to remove repression) and glucose is absent (to activate CAP-cAMP complex), leading to strong transcription of the lac genes.