Molecular Biology and Gene Regulation

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

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.