16. Regulation of Expression

The Lac Operon

Predict what would happen to regulation of the lac operon if the lacI gene were moved 50,000 nucleotides upstream of its normal location.

Gene Regulation and the Lac Operon

In the Absence of Lactose

Lac Operon

The lac operon is a(n) _______________ operon that is typically ______________.

X-gal is a colorless, lactose-like molecule that can be split into two fragments by ββ-galactosidase. One of these product molecules creates a blue color. The photograph here shows E. coli colonies growing in a medium that contains X-gal. Find three colonies whose cells have functioning copies of ββ-galactosidase. Find three colonies whose cells might have mutations in the lacZ or the lacY genes. Suppose you analyze the protein-coding sequence of the lacZ and lacY genes of cells from the three mutant colonies and find that these sequences are wild type (normal). What other region of the lac operon might be altered to account for the mutant phenotype of these colonies?

Animation: The lac Operon in E. coli 

Gene Regulation lac operon

The protein that binds to the operator of the lac operon to prevent transcription is encoded by which gene?

It serves no function in regulating the lac operon.

In the lac operon, which of the following functions does the lactose molecule serve:

Why are the genes involved in lactose metabolism considered to be an operon?
a. They occupy adjacent locations on the E. coli chromosome.
b. They have a similar function.
c. They are all required for normal cell function.
d. They are all controlled by the same promoter.

IPTG is a molecule with a structure much like lactose. IPTG can be transported into cells by galactoside permease and can bind to the lac repressor protein. However, unlike lactose, IPTG is not broken down by ββ-galactosidase. Predict what would occur to lac operon regulation if IPTG were added to E. coli growth medium containing no glucose or lactose.

In the Presence of Lactose

The repressor will bind the operator allowing transcription of the lac operon genes.

The repressor will not bind the operator preventing transcription of the lac operon genes.

The repressor will not bind the operator allowing transcription of the lac operon genes.

The repressor will bind the operator preventing transcription of the lac operon genes.

If E. coli bacteria are grown in the presence of lactose:

Evaluate these statements about regulation of the lac operon. Select True or False for each statement.
T/F The lac operon is transcribed at the highest rate when extracellular glucose and lactose are abundant.
T/F The repressor protein is bound to DNA of the operator when lactose is present.
T/F A mutation in the operator is likely to prevent transcription of the lac operon under any condition.
T/F A mutation that alters the catabolite activator protein is predicted to alter the regulation of many different operons.

 No. The repressor protein is already present and bound to the operator. 

 No. The operator is a nucleotide sequence. 

 No. A bacterial cell will not know what to do with human growth factor. 

 No. Prokaryotes do not use transcription factors. 

The operon is still regulated as the lac operon.

You have inserted the gene for human growth factor into the E. coli lactose operon, replacing the structural genes with the gene for human growth factor. What substance must you add to your culture of bacteria to cause them to produce human growth factor for you?

Prokaryotic Gene Regulation: Lac Operon

Learn the toughest concepts covered in Biology1&2 with step-by-step video tutorials and practice problems by world-class tutors 

Jason

General Biology

https://static.studychannel.pearsonprd.tech/courses/biology/thumbnails/biology

#FFFFFF

AMBOSS: Medical Knowledge Distilled

Jason Amores Sumpter

Steve Gorsich

Andrey K

PremedHQ Science Academy

1. Introduction to Biology

2. Chemistry

3. Water

4. Biomolecules

5. Cell Components

6. The Membrane

7. Energy and Metabolism

8. Respiration

9. Photosynthesis

10. Cell Signaling

11. Cell Division

12. Meiosis

13. Mendelian Genetics

14. DNA Synthesis

15. Gene Expression

17. Viruses

18. Biotechnology

19. Genomics

20. Development

21. Evolution by Natural Selection

22. Evolution of Populations

23. Speciation

24. History of Life on Earth

25. Phylogeny

26. Prokaryotes

27. Protists

28. Plants

29. Fungi

30. Overview of Animals

31. Invertebrates

32. Vertebrates

33. Plant Anatomy

34. Vascular Plant Transport

35. Soil

36. Plant Reproduction

37. Plant Sensation and Response

38. Animal Form and Function

39. Digestive System

40. Circulatory System

41. Immune System

42. Osmoregulation and Excretion

43. Endocrine System

44. Animal Reproduction

45. Nervous System

46. Sensory Systems

47. Muscle Systems

48. Ecology

49. Animal Behavior

50. Population Ecology

51. Community Ecology

52. Ecosystems

53. Conservation Biology

[BOOK BIO] CLUTCH

Review of the Lac Operon & Trp Operon

Eukaryotic Transcriptional Control

Glucose's Impact on Lac Operon

Prokaryotic Gene Regulation via Operons

The Trp Operon

Introduction to Eukaryotic Gene Regulation

Eukaryotic Post-Translational Regulation

Eukaryotic Post-Transcriptional Regulation

Eukaryotic Chromatin Modifications

Introduction to Regulation of Gene Expression

General Chemistry

Jules

Study the key concepts of Physics with descriptive videos, questions, and more

Physics

Patrick

Financial Accounting

Brian

Dive deep into Psychology with videos, practice problems, and more.

Psychology

Microeconomics

The first in a two-course sequence introduces the basic structure and functions of the human body

Anatomy & Physiology

College Algebra covers algebraic topics and skills necessary to succeed in college-level math

College Algebra

Organic Chemistry

Johnny

Genetics

Kylia

GOB Chemistry

Microbiology

Cell Biology

Analytical Chemistry

Study topics incliding trogonometric functions, identities and equations, solutions of triangles, complex numbers, and other topics as time permits

Trigonometry

Learn the toughest concepts covered in Precalculus with step-by-step video tutorials and practice problems by world-class tutors

Precalculus

Biochemistry

Macroeconomics

Chemistry

Biology

Math

Business

Social Sciences

Michelle Barry Franco

Building Great Presentations

Eric Zackrison, PhD

Critical Thinking And Problem Solving

Sam Bennett

Embracing Times Of Uncertainty

Nicole Tetreault, PhD

Emotional Intelligence Basics

Eugene Choi, PharmD

Enhancing Your Critical Thinking Skills

Jason Richardson, PsyD

Habits To Win Every Day

Alyssa Lowery, PhD

Having Powerful Advanced Conversations

Don Gilman, EdD

How To Influence & Persuade

Amy Matthews

Leadership Skills For Rising Stars

Listening To Lead

Michael Shermer, PhD

Making Decisions Under Uncertainty

Lynne Hurdle

Mistakes To Avoid When Resolving Conflict

Michael Veltri

Overcoming Decision Making Traps

Mike Vardy

Prioritizing Effectively

Secrets Of Effective Prioritization

Strategies To Build Up Your Creativity

Tools For Decision Making

Tutti Taygerly

Unleash And Advance Your Creativity

Winning Collaboration: How To Work More Effectively With Different Personalities

Writing Emails People Want To Read

Critical Thinking

Self Management

Digital Literacy

Collaboration

Communication

Analytical Thinking

Leadership

Flexibility/Adaptability

Innovation

Eric Zackrison

Nicole Tetreault

Dive deep into Python with videos and more.

Introduction to Python

Arianne Dee

Agile Project and Product Management

Agile & Product Management

Mariya Breyther 

Introduction to Microsoft Power BI

Microsoft Power BI

Chris Sorensen

Data Analysis Fundamentals with Excel

Data Analysis - Excel

Chris Sorensen & Ammul Shergill

Getting Started with  and Cryptocurrency

Introduction to Blockchain

George Levy

Learn Enough HTML, CSS and Layout to be Dangerous

HTML, CSS & Layout

Lee Donahoe & Michael Hartl

Learn Enough JavaScript to be Dangerous: A Tutorial Introduction to Programming with JavaScript

Introduction to JavaScript

Michael Hartl

Watch next