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 statement best describes the lac operon in E. coli?

It is an operon that controls the synthesis of ribosomal RNA.

It is a repressible operon that is always active unless tryptophan is present.

It is a set of genes that are transcribed only when glucose is abundant.

It is an inducible operon that is activated in the presence of lactose and absence of glucose.

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Verified step by step guidance

Understand what an operon is: an operon is a cluster of genes under the control of a single promoter and regulatory elements, allowing coordinated expression.

Recall that the lac operon in E. coli is involved in the metabolism of lactose, a sugar that can be used as an energy source when glucose is not available.

Recognize that the lac operon is an inducible operon, meaning it is usually off but can be turned on (induced) in response to the presence of lactose.

Note that the lac operon is activated when lactose is present (which acts as an inducer by inactivating the repressor) and glucose is absent (which relieves catabolite repression), allowing transcription of genes needed to metabolize lactose.

Compare the given statements to these characteristics to identify the correct description: the lac operon is not involved in ribosomal RNA synthesis, is not repressible by tryptophan, and is not active when glucose is abundant.