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 diagrams best represents a system in which the lac operon genes are about to be transcribed?

Lactose is present, and the repressor is not bound to the operator.

Lactose is absent, and the repressor is bound to the operator.

Lactose is present, but the repressor is still bound to the operator.

Glucose is present, and the repressor is bound to the operator.

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Verified step by step guidance

Step 1: Understand the role of the lac operon in gene regulation. The lac operon controls the expression of genes involved in lactose metabolism in bacteria, and its transcription depends on the presence or absence of lactose and glucose.

Step 2: Recall that the lac operon is normally repressed by a repressor protein that binds to the operator region, preventing transcription when lactose is absent.

Step 3: When lactose is present, it acts as an inducer by binding to the repressor, causing a conformational change that prevents the repressor from binding to the operator. This allows RNA polymerase to transcribe the lac operon genes.

Step 4: Consider the effect of glucose presence. High glucose levels inhibit the activation of the lac operon through catabolite repression, but the key factor for transcription initiation is that the repressor must not be bound to the operator.

Step 5: Conclude that the lac operon genes are about to be transcribed when lactose is present and the repressor is not bound to the operator, allowing RNA polymerase to access the promoter and initiate transcription.