Molecular Biology and Gene Regulation

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Questions and Answers

What role do chromatin writer complexes serve in relation to histones?

Regulate histone modifications (correct)

Silence gene expression

Promote transcription of mRNA

Repair damaged DNA strands

Which statement correctly describes histone acetylation?

It is carried out by chromatin erasers.

It causes increased transcriptional silencing.

It is mainly performed on serines.

It tends to open up chromatin. (correct)

What is the function of small interfering RNAs (siRNAs)?

To repair RNA damage

To mimic miRNA and induce silencing (correct)

To bind to regulatory DNA sequences

To enhance gene transcription

What is the result of DNA methylation?

Transcriptional silencing Signup and view all the answers

Which type of RNA primarily regulates mRNA transcription?

MicroRNA Signup and view all the answers

Which feature is associated with heterochromatin?

Transcriptionally inactive Signup and view all the answers

What do mobile genetic elements, like transposons, primarily contribute to?

Encouraging genetic diversity and mutation Signup and view all the answers

What is the primary outcome of gene promoter activity?

Enhancing RNA polymerase binding Signup and view all the answers

What role does the XIST gene play in gene expression modulation?

It forms a cloak of inactivation on chromosomes. Signup and view all the answers

How do histone modifications relate to gene expression?

They can act as scaffolds that stabilize protein complexes. Signup and view all the answers

What is the function of the CRISPR-Cas system in bacteria?

It integrates foreign DNA into the bacterial genome. Signup and view all the answers

What characterizes the plasma membrane's structure?

It is a fluid bilayer of amphipathic phospholipids. Signup and view all the answers

What are lipid rafts known for?

They contain specialized protein domains. Signup and view all the answers

How does guide RNA (gRNA) function in the CRISPR technology?

It directs a Cas nuclease to a targeted DNA sequence. Signup and view all the answers

Which of the following describes tight junctions in epithelial cells?

They maintain cell polarity through intercellular interactions. Signup and view all the answers

What constitutes the extracellular surface of cells?

Components enlarged by carbohydrate structures called glycocalyx. Signup and view all the answers

Study Notes

The Genome

Non-coding DNA includes promoters, enhancers, regulatory RNAs, mobile genetic elements (transposons), telomeres, and centromeres
Histones form nucleosomes, which wrap around 147 base pairs of DNA
Heterochromatin is transcriptionally inactive, while euchromatin is active
Histone modifications (methylation, acetylation, phosphorylation) regulate gene expression
DNA methylation leads to transcriptional silencing
MicroRNAs (miRNAs) regulate mRNA transcription, with each gene potentially regulating multiple exons
MicroRNAs are processed into mature single-stranded miRNAs by "Dicer" and associate with RISC, potentially cleaving target mRNAs
Long noncoding RNAs (lncRNAs) significantly modulate gene expression
Gene editing utilizes CRISPR-Cas systems, repurposing a bacterial DNA-sampling system
Guide RNAs direct Cas9 to target DNA sequences, allowing gene silencing

Cellular Housekeeping

Plasma membranes are fluid bilayers with asymmetrical phospholipid distribution
Lipid rafts are specialized membrane domains enriched in cholesterol and glycosphingolipids
Extracellular surfaces are decorated with carbohydrates (glycocalyx)
Proteins/glycoproteins facilitate transport and interactions
Proteins can be modified post-translationally
Passive diffusion transports nonpolar molecules across membranes
Active transport uses energy to move molecules against concentration gradients via carriers
Endocytosis (pinocytosis, phagocytosis) internalizes substances
Exocytosis releases substances
Transcytosis transports substances through cells via vesicles
Cytoskeletal proteins (actin microfilaments, intermediate filaments, microtubules) provide structural support and facilitate movement

Endoplasmic Reticulum & Golgi Apparatus

Rough ER has ribosomes for protein synthesis, folding, and complex formation
Misfolded proteins are degraded
Golgi apparatus processes and modifies proteins
Protein modification includes addition of N-linked and O-linked oligosaccharides
Smooth ER is abundant in cells with steroid hormone production
Lysosomes break down cellular components
Proteasomes degrade tagged proteins

Metabolism & Mitochondria

Mitochondria play key roles in energy production, oxidative metabolism, and intermediate metabolism
Mitochondrial DNA is mostly maternally inherited
Rapidly dividing cells may exhibit the Warburg effect
External injury can damage mitochondria, potentially triggering cell death (necrosis) or apoptosis

Cellular Activation

Signal transduction pathways involve cell-surface receptors (ion channels, G-protein-coupled receptors, tyrosine kinases) and intracellular receptors
Ligands bind to high-affinity receptors, initiating intracellular events
Receptors can have intrinsic kinase activity or involve non-receptor tyrosine kinases
Transcription factors bind to DNA to regulate gene expression
Growth factors stimulate cell cycle entry
Extracellular matrix provides structural support and regulates cell proliferation

Cytoskeletal Proteins

Actin microfilaments, intermediate filaments and microtubules give cells structural support and facilitate movement within the cell
Microtubules are used in movement, particularly of vesicles

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Description

Explore the intricate mechanics of non-coding DNA, histones, and gene expression regulation. This quiz covers key concepts such as microRNAs, long noncoding RNAs, and CRISPR-Cas systems. Test your understanding of molecular structures and their roles in genetic regulation.