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Ch. 8 - Microbial Genetics
Tortora - Microbiology: An Introduction 14th Edition
Tortora14th EditionMicrobiology: An IntroductionISBN: 9780138200398Not the one you use?Change textbook
All textbooksTortora 14th EditionCh. 8 - Microbial GeneticsProblem 8
Chapter 8, Problem 8

Use the following choices to answer the question:
a. Catabolite repression
b. DNA polymerase
c. Induction
d. Repression
e. Translation


The mechanism by which lactose controls the lac operon.

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1
Step 1: Understand the lac operon system, which is a set of genes involved in the metabolism of lactose in bacteria such as Escherichia coli.
Step 2: Recognize that the lac operon is regulated by the presence or absence of lactose, which acts as an inducer molecule.
Step 3: Identify that when lactose is present, it binds to the repressor protein, causing a conformational change that prevents the repressor from binding to the operator region of the operon.
Step 4: This removal of the repressor from the operator allows RNA polymerase to transcribe the genes needed for lactose metabolism, a process known as induction.
Step 5: Therefore, the mechanism by which lactose controls the lac operon is best described by the term 'induction' from the given choices.

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Key Concepts

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

Induction

Induction is a regulatory mechanism where the presence of a specific molecule, such as lactose, triggers the expression of certain genes. In the lac operon, lactose acts as an inducer by binding to the repressor protein, causing it to release from the operator and allowing transcription to proceed.
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Lac Operon Structure and Function

The lac operon is a set of genes involved in lactose metabolism in bacteria. It includes structural genes, a promoter, an operator, and a repressor gene. The operon is regulated to ensure that enzymes for lactose breakdown are produced only when lactose is available.
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Repression

Repression is a gene regulation mechanism where a repressor protein binds to the operator region of an operon, blocking RNA polymerase and preventing transcription. In the absence of lactose, the lac repressor binds to the operator, inhibiting expression of the lac operon genes.
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Related Practice
Textbook Question

Identify when (before transcription, after transcription but before translation, after translation) each of the following regulatory mechanisms functions.

a. ATP combines with an enzyme, altering its shape.

b. A short RNA is synthesized that is complementary to mRNA.

c. Methylation of DNA occurs.

d. An inducer combines with a repressor.

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Textbook Question

Use the following choices to answer the question:

a. Catabolite repression

b. DNA polymerase

c. Induction

d. Repression

e. Translation


Mechanism by which the presence of glucose inhibits the lac operon.

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Textbook Question

Two offspring cells are most likely to inherit which one of the following from the parent cell?

a. A change in a nucleotide in mRNA

b. A change in a nucleotide in tRNA

c. A change in a nucleotide in rRNA

d. A change in a nucleotide in DNA

e. A change in a protein

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Textbook Question

Which sequence is the best target for damage by UV radiation: AGGCAA, CTTTGA, or GUAAAU? Why aren’t all bacteria killed when they are exposed to sunlight?

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Textbook Question

You are provided with cultures with the following characteristics:

Culture 1: F+, genotype A+B+C+

Culture 2: F ̄, genotype A ̄B ̄C ̄

a. Indicate the possible genotypes of a recombinant cell resulting from the conjugation of cultures 1 and 2.

b. Indicate the possible genotypes of a recombinant cell resulting from conjugation of the two cultures after the F+ has become an Hfr cell.

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Textbook Question

Why are mutation and recombination important in the process of natural selection and the evolution of organisms?

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