Table of contents

1. Introduction to Biology2h 42m
2. Chemistry3h 37m
3. Water1h 26m
4. Biomolecules2h 23m
5. Cell Components2h 26m
6. The Membrane2h 31m
7. Energy and Metabolism2h 0m
8. Respiration2h 40m
9. Photosynthesis2h 49m
10. Cell Signaling59m
11. Cell Division2h 47m
12. Meiosis2h 0m
13. Mendelian Genetics4h 44m
14. DNA Synthesis2h 27m
15. Gene Expression3h 6m
16. Regulation of Expression3h 31m
17. Viruses37m
- Viruses
  37m
18. Biotechnology2h 58m
19. Genomics17m
- Genomes
  17m
20. Development1h 5m
21. Evolution3h 1m
22. Evolution of Populations3h 53m
23. Speciation1h 37m
24. History of Life on Earth2h 6m
25. Phylogeny2h 31m
26. Prokaryotes4h 59m
27. Protists1h 12m
28. Plants1h 22m
29. Fungi36m
- Fungi
  19m
- Fungi Reproduction
  17m
30. Overview of Animals34m
- Overview of Animals
  34m
31. Invertebrates1h 2m
32. Vertebrates50m
33. Plant Anatomy1h 3m
34. Vascular Plant Transport1h 2m
- Water Potential
  1h 2m
35. Soil37m
- Soil and Nutrients
  20m
- Nitrogen Fixation
  16m
36. Plant Reproduction47m
- Flowers
  33m
- Seeds
  14m
37. Plant Sensation and Response1h 9m
38. Animal Form and Function1h 19m
39. Digestive System1h 10m
- Digestion
  1h 3m
- Blood Sugar Homeostasis
  7m
40. Circulatory System1h 49m
41. Immune System1h 12m
42. Osmoregulation and Excretion50m
- Osmoregulation and Excretion
  50m
43. Endocrine System1h 4m
- Endocrine System
  1h 4m
44. Animal Reproduction1h 2m
- Animal Reproduction
  1h 2m
45. Nervous System1h 55m
- Neurons and Action Potentials
  1h 8m
- Central and Peripheral Nervous System
  46m
46. Sensory Systems46m
- Sensory System
  46m
47. Muscle Systems23m
- Musculoskeletal System
  23m
48. Ecology3h 11m
49. Animal Behavior28m
- Animal Behavior
  28m
50. Population Ecology3h 41m
51. Community Ecology2h 46m
52. Ecosystems2h 36m
53. Conservation Biology24m
- Conservation Biology
  24m

16. Regulation of Expression

Prokaryotic Gene Regulation via Operons

General Biology

16. Regulation of Expression

Prokaryotic Gene Regulation via Operons

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1:47 minutes

Problem 2

Textbook Question

In the lac operon, the repressor inhibits transcription whena. the repressor is bound to the inducer.b. the repressor is not bound to the inducer.c. the repressor is bound to glucose.d. the repressor is not bound to the operator.

Verified step by step guidance

Understand the function of the lac operon: The lac operon is a set of genes in bacteria that are involved in the metabolism of lactose. It is regulated by several components including the repressor protein, which plays a crucial role in controlling the transcription of the operon.

Identify the role of the repressor: The repressor protein can bind to the operator region of the lac operon, thereby blocking RNA polymerase from transcribing the downstream genes necessary for lactose metabolism.

Consider the effect of the inducer on the repressor: The inducer (allolactose, a derivative of lactose) binds to the repressor. When the inducer is bound to the repressor, it causes a conformational change in the repressor.

Analyze the conformational change: This change in shape of the repressor reduces its affinity for the operator region, preventing it from binding effectively.

Conclude the correct condition for inhibition: Since the binding of the inducer to the repressor prevents the repressor from binding to the operator, transcription is inhibited when the repressor is not bound to the inducer.

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Key Concepts

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

Lac Operon Structure

The lac operon is a set of genes in E. coli that are involved in the metabolism of lactose. It consists of three structural genes (lacZ, lacY, and lacA) and regulatory elements, including a promoter and an operator. The operon is controlled by a repressor protein that binds to the operator region, preventing transcription when lactose is absent.

Repressor Protein Function

The repressor protein is a key regulatory element in the lac operon. It binds to the operator region of the operon, blocking RNA polymerase from transcribing the downstream genes. When lactose is present, it binds to the repressor, causing a conformational change that prevents the repressor from binding to the operator, thus allowing transcription to occur.

Inducer Molecules

Inducers are molecules that trigger the expression of genes by inactivating repressors. In the case of the lac operon, allolactose, a derivative of lactose, acts as the inducer. When allolactose binds to the repressor, it alters the repressor's shape, preventing it from binding to the operator, which leads to the transcription of the lac genes necessary for lactose metabolism.