GRE Subject Test: Biochemistry, Cell, and Molecular Biology : Help with Other Gene Regulation Principles
Study concepts, example questions & explanations for GRE Subject Test: Biochemistry, Cell, and Molecular Biology
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Example Questions
Example Question #11 : Gene Regulation
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?
Oncogene addiction
Oncogenic shock
Synthetic lethality
Apoptosis
Secondary mutations
Synthetic lethality
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.
Example Question #1 : Help With Other Gene Regulation Principles
When modifiying histones with either activating or repressing marks, such as with acetyl and methyl groups, histone acetyltransferases and histone methyltransferases normally modify which amino acid?
Phenylalanine
Alanine
Lysine
Guanine
Aspartic acid
Lysine
Histones are almost always modified on lysines. Acetylation normally is an activating mark, and methylation is normally a repressing mark of chromatin structure.
Note that guanine is not an amino acid, but a nucleotide.
Example Question #1 : Help With Other Gene Regulation Principles
Which of the following is indicative of enhancers in the chromatin landscape of a given cell?
DNase1 hypersensitive sites
All of the other answers are correct
H3K4me1 histone marks
H3K4me1 and H3K27Ac histone marks
H3K4me1 and H3K27me3 histone marks
All of the other answers are correct
The correct answer is all of the other answers are correct. H3K4me1 (Histone 3 Lysine 4 methyl 1) marks where enhancers are in the chromatin landscape. By further identifying H3K27Ac or H3K27Me3 marks on the same histone, we can determine whether the enhancer is active or inactive, respectively. A DNase 1 hypersensitivity assay will preferentially cut open chromatin, which often is indicative of enhancer regions in the chromatin landscape.
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