Gene regulation
60 flashcards covering Gene regulation for the MCAT Biology & Biochemistry section.
Gene regulation is the process by which cells control which genes are active or inactive at any given time. This allows organisms to produce the right proteins in the right amounts, adapting to their environment, developing from a single cell into a complex body, and maintaining health. For instance, in humans, gene regulation ensures that liver cells make enzymes for detoxification while muscle cells focus on proteins for contraction, all from the same DNA blueprint.
On the MCAT, gene regulation appears in Biology and Biochemistry questions that test mechanisms like transcription factors, operons, and epigenetic changes. Expect multiple-choice items involving experimental data, pathways, or comparisons between prokaryotes and eukaryotes, with common traps like mistaking activators for repressors or ignoring environmental influences. Focus on integrating these concepts with broader topics, such as gene expression in disease or evolution.
Practice sketching regulatory networks from memory.
Terms (60)
- 01
Gene regulation
The process by which cells control the expression of genes to produce the right proteins at the right time, ensuring efficient cellular function and response to environmental changes.
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Operon
A cluster of genes in prokaryotes that are transcribed together under the control of a single promoter, allowing coordinated regulation of related functions.
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Lac operon
A specific operon in E. coli that regulates genes for lactose metabolism, turning on when lactose is present and glucose is absent to conserve energy.
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Repressor
A protein that binds to DNA and prevents transcription of specific genes, acting as a regulatory switch in prokaryotic gene expression.
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Inducer
A molecule that binds to a repressor protein, causing it to detach from DNA and allow transcription of the associated genes.
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Promoter
A region of DNA where RNA polymerase binds to initiate transcription, serving as the starting point for gene expression.
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Operator
A DNA sequence in an operon where a repressor binds to block transcription, controlling whether the genes are expressed.
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Transcriptional regulation
The control of gene expression at the level of transcription, involving factors that influence RNA polymerase's ability to initiate mRNA synthesis.
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Post-transcriptional regulation
The modification of mRNA after transcription, such as through splicing or degradation, to fine-tune protein production.
- 10
RNA interference
A process where small RNA molecules silence gene expression by targeting and degrading specific mRNAs or blocking their translation.
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miRNA
MicroRNA, a small non-coding RNA that binds to mRNA to inhibit its translation or promote its degradation, playing a key role in gene regulation.
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siRNA
Small interfering RNA, which triggers the degradation of specific mRNAs through RNA interference, used in cellular defense and regulation.
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Enhancer
A DNA sequence that increases the transcription of genes by providing binding sites for activator proteins, often located far from the gene.
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Silencer
A DNA element that decreases gene transcription by binding repressor proteins, helping to turn off genes when not needed.
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Transcription factors
Proteins that bind to specific DNA sequences to regulate transcription, either activating or repressing gene expression.
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General transcription factors
A set of proteins required for the assembly of the transcription machinery at the promoter, essential for basic transcription initiation.
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Specific transcription factors
Proteins that bind to enhancer or promoter regions to regulate particular genes in response to signals, enabling targeted gene expression.
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Epigenetic regulation
The heritable changes in gene expression that do not involve alterations to the DNA sequence, such as DNA methylation and histone modification.
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DNA methylation
The addition of methyl groups to DNA, typically at cytosine bases, which generally represses transcription by making chromatin more compact.
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Histone modification
Chemical changes to histone proteins, like acetylation or methylation, that affect chromatin structure and thereby influence gene accessibility for transcription.
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Chromatin remodeling
The process of altering chromatin structure to make DNA more or less accessible for transcription, often involving ATP-dependent complexes.
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Alternative splicing
A mechanism that produces different mRNA variants from the same gene by including or excluding certain exons, increasing protein diversity.
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mRNA stability
The duration that mRNA persists in the cell before degradation, which is regulated to control how much protein is ultimately produced from a gene.
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Translational regulation
The control of protein synthesis at the ribosome, such as through initiation factors or regulatory proteins that affect mRNA translation efficiency.
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Riboswitches
RNA structures in mRNA that change shape in response to small molecules, thereby regulating translation or transcription of the gene.
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Attenuation
A regulatory mechanism in prokaryotes where transcription is terminated early based on the cell's metabolic state, as seen in the trp operon.
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Trp operon
An operon in E. coli that regulates tryptophan synthesis genes, repressing transcription when tryptophan levels are high to prevent overproduction.
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Positive regulation
A type of gene regulation where an activator protein enhances transcription, turning on genes in response to specific signals.
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Negative regulation
Gene regulation that involves repressors inhibiting transcription, ensuring genes are only expressed when necessary.
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Activator
A protein that binds to DNA and promotes transcription by recruiting RNA polymerase or modifying chromatin structure.
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Co-repressor
A molecule that binds to a repressor protein, enabling it to block transcription, often in response to environmental cues.
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Auto-regulation
When a gene product, such as a transcription factor, regulates its own expression, creating a feedback loop for precise control.
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Feedback inhibition in gene regulation
A regulatory mechanism where the end product of a pathway inhibits an earlier step, such as repressing the genes for its own synthesis.
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Heat shock response
A cellular mechanism that upregulates genes for heat shock proteins in response to stress, protecting cells from damage.
- 35
Steroid hormone receptors
Proteins that act as transcription factors when bound to steroid hormones, regulating genes involved in development and metabolism.
- 36
JAK-STAT pathway
A signaling pathway that leads to the activation of transcription factors, regulating genes in response to cytokines and growth factors.
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NF-kB pathway
A signaling cascade that activates transcription factors to regulate genes involved in inflammation and immune responses.
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Gene expression in cell cycle
The regulation of genes that control progression through the cell cycle, ensuring proper DNA replication and division.
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Oncogenes
Genes that, when mutated or overexpressed, promote uncontrolled cell growth by altering normal gene regulation pathways.
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Tumor suppressor genes
Genes that regulate cell growth and division, and when inactivated, allow unchecked proliferation due to loss of regulation.
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X-inactivation
The process in female mammals where one X chromosome is silenced to equalize gene expression between sexes.
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Genomic imprinting
The phenomenon where certain genes are expressed based on whether they are inherited from the mother or father, due to epigenetic marks.
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Barr body
A condensed, inactive X chromosome in female cells, resulting from X-inactivation and serving as a form of dosage compensation.
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Dosage compensation
Mechanisms that balance gene expression between sexes, such as X-inactivation in mammals, to prevent overexpression.
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Common trap: Prokaryotic vs. eukaryotic regulation
Prokaryotes use operons for quick responses, while eukaryotes rely on complex transcription factors and chromatin modifications, so don't confuse the two systems.
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RNA polymerase binding
The initial step in transcription where RNA polymerase attaches to the promoter, regulated by factors that determine gene activation.
- 47
Sigma factor
A subunit of bacterial RNA polymerase that recognizes the promoter sequence, allowing specific gene transcription in response to needs.
- 48
Histone acetylation
The addition of acetyl groups to histones, which loosens chromatin structure and promotes gene transcription by increasing DNA accessibility.
- 49
Exon skipping
A form of alternative splicing where an exon is omitted from the mRNA, leading to different protein isoforms with varied functions.
- 50
MicroRNA biogenesis
The processing of precursor miRNAs into mature forms by enzymes like Dicer, which then regulate target gene expression.
- 51
Constitutive genes
Genes that are continuously expressed at a constant level, unlike regulated genes that vary based on cellular conditions.
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Inducible genes
Genes that are turned on in response to specific signals, such as environmental stressors, to adapt cellular functions.
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Repressible genes
Genes that are normally active but can be turned off by repressors when their products are abundant, preventing waste.
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Transcriptional start site
The exact location on DNA where transcription begins, influenced by regulatory elements that control gene expression accuracy.
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Polyadenylation
The addition of a poly-A tail to mRNA, which affects its stability and export, as part of post-transcriptional regulation.
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RNA editing
The alteration of specific nucleotides in RNA after transcription, changing the coding sequence and thus the resulting protein.
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Trans-acting factors
Molecules, like transcription factors, that bind to DNA from a distance and regulate gene expression without being part of the gene sequence.
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Cis-acting elements
DNA sequences, such as promoters or enhancers, that regulate the expression of genes on the same chromosome.
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Gene silencing
The complete suppression of gene expression, often through epigenetic mechanisms or RNA interference, to maintain cellular identity.
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Developmental gene regulation
The precise control of gene expression during embryonic development, guiding cell differentiation and tissue formation.