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Questions and Answers
What is the primary function of messenger RNA (mRNA) in the cell?
What is the primary function of messenger RNA (mRNA) in the cell?
Which sugar component distinguishes RNA from DNA?
Which sugar component distinguishes RNA from DNA?
What replaces thymine in RNA?
What replaces thymine in RNA?
What are ribozymes primarily associated with?
What are ribozymes primarily associated with?
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Which structure is formed by pairing bases within approximately 5-10 nucleotides in RNA?
Which structure is formed by pairing bases within approximately 5-10 nucleotides in RNA?
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Where does the synthesis of mRNA occur within a eukaryotic cell?
Where does the synthesis of mRNA occur within a eukaryotic cell?
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What is the flow of genetic information in a cell?
What is the flow of genetic information in a cell?
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Which of the following best describes the uniqueness of most cellular RNAs compared to DNA?
Which of the following best describes the uniqueness of most cellular RNAs compared to DNA?
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What role do helicases play during DNA replication?
What role do helicases play during DNA replication?
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How do single-strand DNA-binding proteins (SSBPs) function during DNA replication?
How do single-strand DNA-binding proteins (SSBPs) function during DNA replication?
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What is the primary function of topoisomerase in DNA replication?
What is the primary function of topoisomerase in DNA replication?
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What is the nature of the initial nucleotide chain produced during DNA synthesis?
What is the nature of the initial nucleotide chain produced during DNA synthesis?
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Why is the sliding clamp necessary during DNA synthesis?
Why is the sliding clamp necessary during DNA synthesis?
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What happens to the DNA strands after the helicase separates them?
What happens to the DNA strands after the helicase separates them?
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What is the consequence of unzipping the helical molecule during replication?
What is the consequence of unzipping the helical molecule during replication?
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Which enzyme initiates the synthesis of RNA primers during DNA replication?
Which enzyme initiates the synthesis of RNA primers during DNA replication?
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What initiates the synthesis of a new RNA chain during DNA replication?
What initiates the synthesis of a new RNA chain during DNA replication?
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Which end of the RNA primer does the new DNA strand begin to elongate from?
Which end of the RNA primer does the new DNA strand begin to elongate from?
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How do DNA polymerases contribute to the elongation of a new DNA strand?
How do DNA polymerases contribute to the elongation of a new DNA strand?
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What provides the energy required for the polymerization reaction during DNA replication?
What provides the energy required for the polymerization reaction during DNA replication?
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What is the role of pyrophosphate in the DNA replication process?
What is the role of pyrophosphate in the DNA replication process?
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Which of the following statements about eukaryotic DNA polymerases is correct?
Which of the following statements about eukaryotic DNA polymerases is correct?
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Which component is involved in forming a phosphodiester bond during DNA synthesis?
Which component is involved in forming a phosphodiester bond during DNA synthesis?
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Which of the following statements accurately describes a function of RNA primers in DNA replication?
Which of the following statements accurately describes a function of RNA primers in DNA replication?
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Study Notes
Introduction to Medical Biology and Genetics
- Course taught by Dr. Hilal Eren Gözel
- Contact information provided: email address and office location
Universal Features of Cells
- More than 10 million species exist on Earth.
- All species reproduce, creating copies of themselves (heredity).
- Hereditary information controls complex chemical processes crucial for cell organization and survival.
- All organisms, whether unicellular or multicellular, originate from a single cell.
- This single cell carries all the hereditary information defining the species.
- All cells use the same chemical code system for hereditary information: DNA (or RNA for viruses).
- DNA or RNA codes (A, C, G, T or U) are universal across all organisms.
- Mechanisms for reading and replicating hereditary information are similar in different species.
- All cells use proteins as catalysts to increase the rate of chemical reactions.
- All cells utilize ATP as their primary energy source.
- All cells are enclosed by a plasma membrane through which nutrients and waste pass.
- All cells have ribosomes.
Differences of Cells
- Size
- Shape
- Chemical requirements
Taxonomic Hierarchy
- The scientific study of classifying living things is called taxonomy.
- This hierarchy is a tiered structure shown as a pyramid;
- Species
- Genus
- Family
- Order
- Class
- Phylum
- Kingdom
Classification of Humans
- Domain – Eukaryota
- Kingdom – Animalia
- Phylum – Chordata
- Class - Mammalia
- Order - Primata
- Family – Hominidae
- Genus – Homo
- Species – Homo sapiens
- The binomial nomenclature system uses two names to uniquely identify each species.
Divisions of Life
- Cells are the basic structural and functional units of all organisms.
- Two major cell types: prokaryotic and eukaryotic.
- Prokaryotic: Bacteria and Archaea
- Eukaryotic: Protists, fungi, animals, and plants
- Prion, Viroid and Virus are additional divisions.
Prokaryotic vs. Eukaryotic Cells
- Prokaryotic:
- No nuclear membrane (nucleoid)
- No membrane-enclosed organelles
- Cell wall: typically complex (e.g., peptidoglycan in bacteria)
- Plasma membrane: lacks sterols in general
- Cytoplasm: simpler cytoskeleton
- Ribosomes : Smaller (70S)
- Single circular DNA, lacks histones
- Cell division: Binary fission
- Reproduction: No meiosis; transfer of DNA fragments only (conjugation)
- Eukaryotic:
- True nucleus, enclosed by a nuclear membrane
- Membrane-enclosed organelles: lysosomes, Golgi complex, ER, mitochondria, chloroplasts (in plant cells)
- Cell wall (when present): chemically simpler
- Plasma membrane: sterols and carbohydrates (as receptors)
- Cytoplasm: complex cytoskeleton and cytoplasmic streaming
- Ribosomes: larger (80S)
- Linear DNA with histones
- Cell division: Mitosis
- Reproduction: Meiosis
Divisions of Life - Virus
- Viruses are small infectious agents that replicate only inside living cells.
- They reproduce by creating copies of themselves using the host's metabolic processes.
- Typically consists of nucleic acid (DNA or RNA) enclosed in a protein coat (capsid) and sometimes a membranous envelope.
- Lack organelles and have only some genes.
Clinical Correlation: Influenza Viruses
- Seasonal influenza (the flu) is a common upper respiratory infection caused by influenza viruses.
- Influenza spreads easily via coughs and sneezes.
- Vaccination is a key prevention measure.
- Common symptoms include fever, muscle aches, chills, rhinitis, cough, weakness, diarrhea, vomiting, fainting, sore throat, and headache.
World Health Organization (WHO) – Facts
- Millions of seasonal influenza cases occur yearly; thousands of deaths result from the infection.
- Most fatalities occur in young children within developing nations.
- Four viral types (A, B, C, and D) exist.
- Influenza A causes pandemics.
- Influenza C is less serious, while Influenza D primarily affects cattle.
Influenza A viruses
- Classified by subtypes based on the properties and combinations of their surface proteins (HA, NA).
- RNP: Ribonucleoprotein complex
- HA binds to receptors on host cells facilitating attachment to cell surface.
- NA cleaves sialic acid from viral receptors.
Influenza Viruses – Subtypes, Clades, and Sub-Clades
- Subtypes: Swine Flu A(H1N1) and A(H3N2)
- Class B: Influenza B(Victoria) and B(Yamagata)
- Clades (groups) and sub-clades.
Levels of Organization
- A hierarchical structure, progressing from atoms to molecules, macromolecules, organelles, cells, tissue, organ, organ system, and organism.
Cell
- The smallest units retaining characteristics of life; including complex organization, metabolic activity, and reproductive behavior.
- 1665, Robert Hooke observed tiny empty compartments in cork under a microscope.
Cell Theory
- Schleiden (1838): Plant tissues are made of cells.
- Schwann (1839): Animal tissues are made of cells.
- All living organisms are composed of one or more cells.
- Cells are the basic living units of organization for all organisms.
- All cells arise from pre-existing cells.
References & Thank You
- Various scientific articles and text books.
The Cell & Organelles
- Introduction to various cell structures, their functions, and clinical relevance. – –
The Cell – Cytoplasmic Matrix (Cytosol)
- The matrix within the cytoplasm composed of various solutes (like inorganic ions and organic molecules), including intermediates, carbohydrates, lipids, proteins, and RNAs.
- Site of numerous metabolic processes vital to cell's existence (like protein synthesis and nutrient breakdown).
- Consists of inclusions; diverse material not enclosed by a plasma membrane (like crystals, pigment granules, lipids, glycogen).
The Cell - Organelles
- Specialized structures with specific functions.
- Membranous organelles are enclosed by plasma membranes that separate their internal environments from the cytoplasm, while non-membranous organelles lack plasma membranes.
The Cell - Nucleus
- Contains a majority of the cell's genes and is a conspicuous organelle, typically measuring around 5 µm in diameter.
- Components: nuclear membrane, chromatin, and nucleolus.
Nucleus
- The double membrane, called the nuclear envelope, encloses the nucleus and separates it from the cytoplasm.
- The nuclear membrane is a double membrane: each membrane consists of a lipid bilayer.
- Each of the two membranes is a lipid bilayer with associated proteins, & separated by a 20-40 nm gap.
- This envelope is perforated with pore structures approximately 100 nm in diameter to allow entry and exit of various macromolecules
- The nuclear side of the envelope is lined by the nuclear lamina, a netlike array of protein filaments that mechanically supports the nuclear envelope.
Nucleus
- In the nucleus, DNA and proteins form chromatin.
- Chromatin condenses to form discrete chromosomes.
- Typical human cells contain 46 chromosomes.
- Sex cells (eggs and sperm) have half the number (23).
- Heterocromatin is heavily condensed chromatin.
- Euchromatin is lightly staining dispersed chromatin where most transcribed genes are located.
Nucleolus
- A small area within the nucleus.
- Primary site for ribosomal RNA (rRNA) production and assembly.
- Contains DNA coded for rRNA, RNA, and proteins.
Ribosome
- Ribosomes are particles composed of ribosomal RNA and proteins.
- Crucial for protein synthesis. –- Ribosomes can be free in the cytosol or bound to the ER or nuclear envelope.
- Bound ribosomes synthesize proteins for insertion into membranes, packaging into organelles, or for export.
- Free ribosomes make enzymes that catalyze the first steps of sugar breakdown (e.g., Hexokinase).
Clinical Correlation: Ribosome
- Ribosomopathies are diseases arising from alterations in the structure or function of ribosomal components.
- Clinical features may include bone marrow failure and developmental anomalies (among other things) Signs and symptoms can vary greatly. Clinical correlation slides have examples of specific diseases.
The Endoplasmic Reticulum (ER)
- A network of membranous tubules and sacs (cisternae) throughout the cytoplasm.
- Continuous with the nuclear envelope.
- Two major regions:
- Rough ER: Ribosomes stud its surface. Primarily involved in protein synthesis.
- Smooth ER: Lacks ribosomes. Synthesizes lipids, metabolizes carbohydrates, stores calcium, and detoxifies poisons/drugs. –
- Specialized functions include steroid synthesis in animal cells.
The Golgi Apparatus
- Consists of flattened membranous sacs (cisternae).
- Modifies, sorts, and packages proteins from the ER into transport vesicles.
Lysosome
- A membranous sac of hydrolytic enzymes that can digest macromolecules (proteins, fats, polysaccharides, and nucleic acids).
- Enzymes function best in acidic environments.
- Involved in cellular recycling (autophagy) by digesting old/damaged organelles and cellular macromolecules. -- Clinical Correlation discusses lysosomal storage diseases.
Mitochondria
- Have a double membrane (smooth outer and folded inner membrane called cristae).
- Site of cellular respiration; a metabolic process that generates ATP (energy).
- Have their own DNA (mtDNA). –
- Proteins produced by free ribosomes.
- Inner membrane folds into cristae and creates two components, intermembrane space, and mitochondrial matrix, facilitating specific metabolic steps in cellular respiration.
- Clinical correlation discusses specific diseases (e.g., MERRF).
Mitochondrium – Endosymbiont Theory
- Mitochondria and chloroplasts share similarities with bacteria.
- The theory suggests an early eukaryotic cell engulfed a nonphotosynthetic prokaryotic bacteria specializing in oxygen use; this cell developed into a crucial energy-producing component.
Peroxisomes
- Specialized metabolic compartments bounded by a single membrane.
- Produce hydrogen peroxide and convert it to water. Important for metabolism of varied molecules such as fatty acids, which are delivered to mitochondria, and detoxification of compounds like alcohol and other harmful substances.
Centrosome – Centrioles
- Microtubule organizing center, typically located near the nucleus.
- Animal cells have pairs of centrioles composed of nine sets of triplets microtubules in a ring. – Central to microtubule organization and critical for cell division.
Cytoskeleton, ECM, Intercellular Junctions
- This section describes the cytoskeleton components (microtubules, microfilaments, and intermediate filaments); extracellular matrix (ECM), and intercellular junctions (tight junctions, desmosomes, and gap junctions), and their importance for cells structural support, movement, and communication.
Cell Membrane - Structure and Function
- The outermost layer separating the cell from the environment with a typical structure composed of phospholipids forming a bilayer, with embedded membrane proteins.
- Phospholipids are amphipathic molecules with hydrophilic heads and hydrophobic tails arranged in a bilayer.
- Membrane proteins are diverse, providing various functions (transport, enzymatic activity, signal transduction, cell-cell recognition, intercellular joining, attachment to the cytoskeleton, and ECM).
Permeability of the Lipid Bilayer
- A cell must exchange substances with its environment (like gases, waste, nutrients).
- The cell membrane controls the movement of substances into and out of cells regulating molecular traffic.
- Hydrophobic substances rapidly pass through the membrane.
- Polar and charged substances need assistance (like proteins). – Passive membrane transport, including simple diffusion, facilitated diffusion, and osmosis.
- Active transport moves substances against their concentration gradients, needing energy (often supplied by ATP-derived phosphate bonds to protein-based pumps).
Bulk Transport
- Mechanisms that move large substances across the membrane (like vesicles, using energy).
- Exocytosis: transport vesicles fuse with the membrane to export a substance.
- Endocytosis: the cell takes in macromolecules by forming vesicles from the plasma membrane (Phagocytosis, Pinocytosis, and Receptor-mediated).
Introduction to Nucleic Acids
- DNA is the genetic material encoding hereditary information reproduced by all cells in our body.
- DNA dictates the development of traits by directing the processes of DNA replication & RNA synthesis to ultimately control protein synthesis.
How is the DNA structure discovered?
- The presentation covers the history of DNA discovery from the initial experiments and observations leading to the development of various models leading to the double-helical structure of DNA
DNA Replication
- Semiconservative replication: each new DNA molecule contains one old strand and one new strand.
- Replication origins: special sites where replication starts in various kinds of DNA.
- Replication fork: the Y-shaped region where the two parental strands are unwound.
- Replication machinery consisting of several proteins facilitating this unwinding, initiation of the new strands and elongation/completion processes.
- Antiparallel Elongation and the problem of lagging/leading strands.
- The role of telomeres and telomerase in protecting chromosome ends during replication.
Clinical Correlation: Colorectal Cancer
- CRC is a significant health concern. The presentation includes mechanisms like telomere erosion and the activation of telomerase in the development and/or progression of this cancer."
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