GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with Gene Regulation Proteins

Study concepts, example questions & explanations for GRE Subject Test: Biochemistry, Cell, and Molecular Biology

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Example Questions

Example Question #1 : Help With Gene Regulation Proteins

Histone acetyltransferases (HATs) transfer acetyl groups from acetyl CoA to lysine residues on histones. What is the purpose of this transfer?

Possible Answers:

Prevent DNA degredation by endonucleases

Facilitate phosphorylation of these lysines by kinases

Prevent transcription factors from binding to DNA

Signal for ubiquitin-mediated degredation of histones

Promote formation of euchromatin and increase gene expression

Correct answer:

Promote formation of euchromatin and increase gene expression

Explanation:

The correct answer is to promote formation of euchromatin and increase gene expression. Acetylation of histones "relaxes" DNA coiling around histones by reducing the affinity between histones and DNA. This allows transcription factors to bind promoter regions and promote increased gene expression via transcription.

 

Example Question #2 : Help With Gene Regulation Proteins

What is the role of mediator in gene expression?

Possible Answers:

Mediator suppresses transcription by methylating histone lysines

Mediator is not involved in gene expression

Mediator facilitates alternative splicing of newly synthesized mRNA transcripts

Mediator is a thermostable DNA polymerase that replicates DNA in extreme temperatures

Mediator is a coactivator of transcription and serves to recruit transcription factors and RNA polymerase II

Correct answer:

Mediator is a coactivator of transcription and serves to recruit transcription factors and RNA polymerase II

Explanation:

The correct answer is that mediator is a coactivator of transcription and serves to recruit transcription factors and RNA polymerase II. Mediator does not directly initiate transcription; however, by protein-protein interactions, it recruits the necessary proteins to sites of transcription. 

Example Question #3 : Help With Gene Regulation Proteins

NFkB is a transcription factor that is held inactive in the cytoplasm when bound by its inhibitor, IkB. Upstream signaling that activates NFkB causes what effect?

Possible Answers:

Ubiquitin-mediated degradation of IkB, causing a conformational shift in NFkB that renders its DNA-binding domain inaccessible

Ubiquitin-mediated degradation of NFkB 

Ubiquitin-mediated degradation of IkB, allowing NFkB to translocate to the nucleus and initiate transcription

Recruitment of transcription factors and coactivators of transcription to the cytoplasmically sequestered NFkB

Ubiquitin-mediated degradation of NFkB, allowing IkB to translocate to the nucleus and initiate transcription

Correct answer:

Ubiquitin-mediated degradation of IkB, allowing NFkB to translocate to the nucleus and initiate transcription

Explanation:

Upstream signaling, such as from a toll-like receptor, causes IKK to phosphorylate IkB, signaling for its ubiquitin-mediated degradation. Since NFkB is no longer bound by its inhibitor, IkB, it translocates to the nucleus where it binds specific motifs in the genome to recruit other transcriptional machinery and initiate transcription. 

Example Question #4 : Help With Gene Regulation Proteins

Which of the following is not a way in which transcription factors influence gene-specific transcription? 

Possible Answers:

Recruiting DNA polymerase

Recruiting RNA polymerase holoenzyme 

Recruiting other transcription factors

Binding transcription factor-specific DNA motifs

Promoting euchromatin formation

Correct answer:

Recruiting DNA polymerase

Explanation:

The correct answer is recruiting DNA polymerase. DNA polymerase is involved in DNA replication, not transcription. Pioneer transcription factors can bind specific DNA motifs and promote euchromatin formation, allowing other transcription factors to bind the less organized DNA. Transcription factors can recruit other transcription factors and the RNA polymerase holoenzyme to promoters to promote gene-specific transcription. 

All GRE Subject Test: Biochemistry, Cell, and Molecular Biology Resources

1 Diagnostic Test 201 Practice Tests Question of the Day Flashcards Learn by Concept
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