AP Biology Operon Definitions

Questions and Answers

What is a diagram of an operon?

A functioning unit of genomic DNA containing a cluster of genes under the control of a single promoter (correct)

A single gene

An RNA molecule

A type of protein

What is a regulator in genetics?

A substance or process that regulates or controls another, such as a regulatory gene.

What is a repressor?

A regulatory protein that binds to an operator and blocks transcription of the genes of an operon.

What is the function of a promoter?

A region of DNA that initiates transcription of a particular gene. Signup and view all the answers

What is an operator?

A segment of DNA where the repressor binds. Signup and view all the answers

What are structural genes?

Genes coding for the production of specific RNA, proteins, or enzymes not involved in regulation. Signup and view all the answers

What is a corepressor?

A substance that inhibits the expression of genes. Signup and view all the answers

What is an inducer?

A molecule that regulates gene expression by disabling repressors. Signup and view all the answers

What does the Lac operon control?

The breakdown of lactose. Signup and view all the answers

What does the Trp operon code for?

The amino acid tryptophan. Signup and view all the answers

What is positive control in gene expression?

Genes are expressed only when an active regulator protein is present. Signup and view all the answers

What is negative control in gene expression?

Genes are expressed unless switched off by a repressor protein. Signup and view all the answers

What does it mean for a pathway to be repressible?

Transcription ceases when there are excess quantities of the end product of the pathway. Signup and view all the answers

What characterizes anabolic processes?

Constructing or synthesizing molecules from smaller units, usually requiring energy input. Signup and view all the answers

What does it mean for a gene system to be inducible?

The system is activated by an early metabolite in the pathway. Signup and view all the answers

What is catabolism?

Chemical reactions that result in the breakdown of complex molecules into simpler ones. Signup and view all the answers

What is the role of cAMP in gene regulation?

cAMP binds to CRP, allowing it to enhance transcription of specific genes. Signup and view all the answers

What is the function of CAP?

It enhances transcription of sugar-metabolizing operons when bound with cyclic AMP. Signup and view all the answers

What is a mutation?

A permanent alteration in the DNA sequence. Signup and view all the answers

Study Notes

Operon Structure and Function

An operon is a unit of genomic DNA that includes multiple genes controlled by a single promoter, essential for co-transcription.
Structural genes in an operon code for specific proteins or enzymes and are not regulatory.

Regulatory Elements

Regulators are substances or genes that control biological processes, such as growth.
Repressors are proteins that bind to operators to block transcription, thus inhibiting gene expression.
Corepressors inhibit gene expression; in prokaryotes, they are small molecules, while in eukaryotes, they are proteins.
Inducers are molecules that promote gene expression by disabling repressors, allowing transcription to occur.

Promoter and Operator

A promoter is a DNA region that initiates the transcription process, found upstream of the gene's transcription start site.
An operator is a DNA segment where a repressor can bind, preventing transcription when active.

Types of Operons

Lac operon controls lactose breakdown; it is an anabolic repressible operon activated when lactose binds to the repressor.
Trp operon synthesizes tryptophan; it is also a repressible operon, where high levels of tryptophan activate the repressor to block transcription.

Control Mechanisms

Positive Control requires an active regulator protein for gene expression; absence leads to operon inactivity.
Negative Control allows gene expression until suppressed by a repressor protein.

Metabolism and Energy

Repressible systems stop enzyme production when excess product is available, ensuring resource efficiency.
Anabolic processes build complex molecules from smaller units, requiring energy input (e.g., ATP).
Inducible systems activate transcription of enzymes in response to specific metabolites, often through repressor inactivation.
Catabolic reactions break down complex molecules into simpler ones, typically releasing energy.

cAMP and CAP

cAMP receptor protein (CRP) interacts with cAMP and binds to promoter DNA, facilitating gene transcription.
CAP (catabolite activator protein) enhances transcription of operons linked to sugar metabolism when bound with cAMP.

Mutations

Gene mutations lead to permanent alterations in the DNA sequence, potentially impacting gene function and expression.

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Explore key terms related to operons in genetics through this quiz. Gain a deeper understanding of concepts like diagrams of operons and their regulators. Perfect for students preparing for AP Biology!