Gene Regulation and Genomics
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GRE › Gene Regulation and Genomics
What differentiates a LTR retrotransposon and a retrovirus?
Retroviruses encode an envelope protein
LTR retrotransposons cannot move between organisms
Retroviruses are the only ones present in eukaryotes
Retroviruses do not insert DNA into their host
None of these are correct
Explanation
The only difference between most LTR retrotransposons and retroviruses are that retroviruses can encode an envelope protein. Phylogenetic analyses have shown that retrotransposons and retroviruses are extremely closely related, and may be direct ancestors of one another.
What differentiates a LTR retrotransposon and a retrovirus?
Retroviruses encode an envelope protein
LTR retrotransposons cannot move between organisms
Retroviruses are the only ones present in eukaryotes
Retroviruses do not insert DNA into their host
None of these are correct
Explanation
The only difference between most LTR retrotransposons and retroviruses are that retroviruses can encode an envelope protein. Phylogenetic analyses have shown that retrotransposons and retroviruses are extremely closely related, and may be direct ancestors of one another.
What differentiates a LTR retrotransposon and a retrovirus?
Retroviruses encode an envelope protein
LTR retrotransposons cannot move between organisms
Retroviruses are the only ones present in eukaryotes
Retroviruses do not insert DNA into their host
None of these are correct
Explanation
The only difference between most LTR retrotransposons and retroviruses are that retroviruses can encode an envelope protein. Phylogenetic analyses have shown that retrotransposons and retroviruses are extremely closely related, and may be direct ancestors of one another.
Histone acetyltransferases (HATs) transfer acetyl groups from acetyl CoA to lysine residues on histones. What is the purpose of this transfer?
Promote formation of euchromatin and increase gene expression
Facilitate phosphorylation of these lysines by kinases
Signal for ubiquitin-mediated degredation of histones
Prevent transcription factors from binding to DNA
Prevent DNA degredation by endonucleases
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.
Histone acetyltransferases (HATs) transfer acetyl groups from acetyl CoA to lysine residues on histones. What is the purpose of this transfer?
Promote formation of euchromatin and increase gene expression
Facilitate phosphorylation of these lysines by kinases
Signal for ubiquitin-mediated degredation of histones
Prevent transcription factors from binding to DNA
Prevent DNA degredation by endonucleases
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.
Histone acetyltransferases (HATs) transfer acetyl groups from acetyl CoA to lysine residues on histones. What is the purpose of this transfer?
Promote formation of euchromatin and increase gene expression
Facilitate phosphorylation of these lysines by kinases
Signal for ubiquitin-mediated degredation of histones
Prevent transcription factors from binding to DNA
Prevent DNA degredation by endonucleases
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.
Inducible operons are bound by a repressor and turned off under normal conditions. How are these operons turned on?
An inducer molecule binds to and inactivates the repressor
An inducer molecule competes with the repressor for binding to the operator
An activator protein displaces the repressor on the operator
A second repressor protein binds to and represses the repressor
The transcription of the repressor protein is inactivated
Explanation
Negatively regulated operons that are said to be inducible have their operator sequence bound by a repressor molecule normally. That leads to these operons being off normally. For these operons to be turned on and transcribed, a small molecule called an inducer has to bind to and inactivate the repressor protein.
Inducible operons are bound by a repressor and turned off under normal conditions. How are these operons turned on?
An inducer molecule binds to and inactivates the repressor
An inducer molecule competes with the repressor for binding to the operator
An activator protein displaces the repressor on the operator
A second repressor protein binds to and represses the repressor
The transcription of the repressor protein is inactivated
Explanation
Negatively regulated operons that are said to be inducible have their operator sequence bound by a repressor molecule normally. That leads to these operons being off normally. For these operons to be turned on and transcribed, a small molecule called an inducer has to bind to and inactivate the repressor protein.
Inducible operons are bound by a repressor and turned off under normal conditions. How are these operons turned on?
An inducer molecule binds to and inactivates the repressor
An inducer molecule competes with the repressor for binding to the operator
An activator protein displaces the repressor on the operator
A second repressor protein binds to and represses the repressor
The transcription of the repressor protein is inactivated
Explanation
Negatively regulated operons that are said to be inducible have their operator sequence bound by a repressor molecule normally. That leads to these operons being off normally. For these operons to be turned on and transcribed, a small molecule called an inducer has to bind to and inactivate the repressor protein.
Mutations in two or more genes cause cell death, however, a mutation in only one of the genes is not lethal.
Which of the following best describes this phenomenon?
Synthetic lethality
Oncogene addiction
Oncogenic shock
Apoptosis
Secondary mutations
Explanation
Synthetic lethality is the correct answer. The combinatorial effect of multiple mutated genes disrupts homeostasis in cells, inducing cell death. A mutation in only one gene can be compensated for in cells by altering the expression of other genes, such as turning on anti-apoptotic signaling pathways.
Oncogene addiction occurs when a tumor cell relies on the expression of a particular oncogene (mutated gene) for survival.
Oncogenic shock refers to an increase in pro-apoptotic signaling and a decrease in anti-apoptotic signaling upon removal of an oncoprotein.
Apoptosis refers to the process of programmed cell death.
Secondary mutations occur in a cancer cell that is treated with a therapeutic agent to promote resistance to that specific agent.