Chapter 18

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What role do repressors play in gene expression?

They prevent activators from binding to DNA. (correct)

They facilitate the activation of control elements.

They modify the DNA sequence directly.

They enhance the binding of transcription factors.

What is a key feature of co-expressed eukaryotic genes?

They can have different regulatory elements.

They are always clustered in operons.

They are located on the same chromosome.

They share the same combination of control elements. (correct)

How do chromatin loops from different chromosomes contribute to gene expression?

They segregate chromatin for distinct functions.

They enhance the transcription of unrelated genes.

They congregate at sites rich in transcription factors. (correct)

They provide structural support for transcription.

What is the purpose of post-transcriptional regulatory mechanisms?

To allow cells to adjust gene expression quickly. Signup and view all the answers

What is true about the combination of control elements in gene activation?

A specific combination is needed for activation. Signup and view all the answers

What effect does histone acetylation have on chromatin structure?

It promotes transcription by opening up the chromatin. Signup and view all the answers

What is the primary consequence of DNA methylation?

Causes long-term inactivation of genes. Signup and view all the answers

How does genomic imprinting affect gene expression?

It regulates expression of either the maternal or paternal alleles. Signup and view all the answers

Which of the following accurately describes epigenetic inheritance?

It is the transmission of traits through mechanisms independent of nucleotide sequence. Signup and view all the answers

What role do chromatin-modifying enzymes play in gene expression?

They influence the ability of DNA to bind transcription machinery. Signup and view all the answers

What role does feedback inhibition play in enzyme regulation?

It inhibits further synthesis of the product by blocking enzyme activity. Signup and view all the answers

What are control elements in relation to eukaryotic genes?

They serve as binding sites for transcription factors. Signup and view all the answers

What constitutes an operon?

The segment of DNA that contains the operator, promoter, and controlled genes. Signup and view all the answers

What distinguishes general transcription factors from specific transcription factors?

General factors are essential for the transcription of all protein-coding genes. Signup and view all the answers

How does the repressor affect gene transcription?

By binding to the operator and blocking transcription. Signup and view all the answers

Which process is associated with the regulation of gene expression in different cell types?

Transcription factor binding to control elements. Signup and view all the answers

What is the function of a corepressor in gene regulation?

It enhances the repressor's ability to inhibit transcription. Signup and view all the answers

What determines whether the repressor is active or inactive?

The presence of other molecules. Signup and view all the answers

What is the purpose of gene expression regulation in bacteria?

To allow only essential genes to be expressed based on environmental needs. Signup and view all the answers

What is located some distance from the operon and produces the repressor protein?

A separate regulatory gene. Signup and view all the answers

What happens when E. coli has insufficient tryptophan?

It begins the synthesis of tryptophan. Signup and view all the answers

What is the primary role of general transcription factors?

They initiate transcription of all protein-coding genes. Signup and view all the answers

What is an activator in the context of transcription?

A protein that binds to an enhancer and stimulates transcription. Signup and view all the answers

How do specific transcription factors contribute to transcription levels?

They bind to both proximal and distal control elements to enhance transcription. Signup and view all the answers

What helps assemble and position the preinitiation complex at the promoter?

Interactions between bound activators and mediator proteins. Signup and view all the answers

Where are proximal control elements typically located?

Close to the promoter of the gene. Signup and view all the answers

What is the function of the mediator proteins in transcription?

To facilitate interactions between activators and general transcription factors. Signup and view all the answers

What is a characteristic of enhancers in relation to genes?

Each enhancer is typically associated with only one gene. Signup and view all the answers

What is the result of protein-mediated bending of DNA in the transcription process?

It brings bound activators into contact with mediator proteins. Signup and view all the answers

What is typically necessary for the development of full-fledged cancer?

Multiple mutations including an active oncogene Signup and view all the answers

Which genes are commonly implicated in inherited breast cancer?

BRCA1 and BRCA2 Signup and view all the answers

How do tumor viruses contribute to cancer development?

By integrating into the DNA and interfering with gene regulation Signup and view all the answers

Which of the following cancers is particularly known for routine screening and removal of suspicious polyps?

Colorectal cancer Signup and view all the answers

What is a characteristic feature of breast cancer as mentioned in the content?

It has four major types identified through genomic profiling Signup and view all the answers

What is the significance of alternative RNA splicing in eukaryotic cells?

It expands the range of proteins that can be produced from a limited number of genes. Signup and view all the answers

Which mechanism is mentioned as blocking the initiation of translation?

Regulatory proteins and miRNA Signup and view all the answers

How does the life span of eukaryotic mRNA compare to that of prokaryotic mRNA?

Eukaryotic mRNA is more long-lived than prokaryotic mRNA. Signup and view all the answers

What role does ubiquitin play in protein regulation?

It marks proteins for degradation by proteasomes. Signup and view all the answers

What regulates the simultaneous activation of translation initiation factors in a cell?

Fertilization processes Signup and view all the answers

Which of the following processes occurs after the translation of polypeptides?

Selective degradation Signup and view all the answers

Where do nucleotide sequences that influence mRNA life span reside in eukaryotes?

In the untranslated region at the 3' end Signup and view all the answers

Which modifications are involved in the processing of polypeptides after translation?

Cleavage and chemical modifications Signup and view all the answers