Molecular Biology: Transcription and Translation

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Questions and Answers

Which component of the replisome is responsible for removing over-spiralization in DNA?

DNA polymerase III

Primase

DNA gyrase (correct)

Helicase

What forms the active RNA polymerase enzyme known as the holoenzyme?

α2ββ′

ββ′ω

α2ββ′ωσ (correct)

αββ′ω

During transcription initiation, what allows RNA polymerase to recognize the promoter region?

Single-stranded DNA binding protein

The stem-loop structure

The core enzyme

The sigma factor (correct)

What causes the termination of transcription in prokaryotes?

Formation of the stem-loop structure in RNA Signup and view all the answers

Which of the following statements is true about prokaryotic mRNAs?

They can have several open reading frames. Signup and view all the answers

What is the function of tRNA during translation?

To carry amino acids to the ribosome Signup and view all the answers

What is the size of the small ribosomal subunit in prokaryotes?

30S Signup and view all the answers

Which nucleotide sequence signals the start of translation?

AUG Signup and view all the answers

What is the primary function of ppGpp in bacteria during amino acid starvation?

It promotes transcription initiation at specific gene promoters Signup and view all the answers

Which enzyme is responsible for synthesizing ppGpp from GTP/GDP and ATP?

RelA Signup and view all the answers

What happens to the σ-70 factor when ppGpp is synthesized?

It is removed from the polymerase Signup and view all the answers

In stress conditions, how does ppGpp influence RNA polymerase activity?

By interacting with alternative σ-factors Signup and view all the answers

What does the EF-tu protein do under conditions of amino acid scarcity?

It halts ribosome activity Signup and view all the answers

What role does DksA play in relation to ppGpp?

It enhances interaction of RNA polymerase with σ-factors Signup and view all the answers

Which component is NOT a part of the signaling pathway described in the content?

Transcription Factor Signup and view all the answers

What triggers the catalytic activity of RelA?

Insufficient charged tRNAs Signup and view all the answers

What is the role of lysozyme in the lifecycle of a phage?

To cleave the peptidoglycan of the bacterial cell wall Signup and view all the answers

Which event occurs during lysogeny of a phage like Lambda?

Phage DNA integrates into the host genome Signup and view all the answers

What triggers the transition from lysogeny to the lytic cycle in a Lambda phage?

Induction caused by stress conditions Signup and view all the answers

What is integrase's function in the context of phage Lambda?

To assist in the integration of phage DNA into the host genome Signup and view all the answers

What occurs to the lambda genome after the infection of a host cell?

It becomes circular due to its cohesive ends Signup and view all the answers

Which of the following is NOT a regulatory gene in the lambda phage?

gal Signup and view all the answers

What is the primary function of the cohesive ends (cos) of the lambda genome?

To allow the linear genome to circularize Signup and view all the answers

Which operon is involved in biotin biosynthesis and is located near the lambda phage integration site?

bio-operon Signup and view all the answers

What is the primary characteristic of endotoxins as described in the content?

Moderately toxic and induce a strong fever Signup and view all the answers

Which sequence correctly describes the interaction of LPS with the immune system?

LPS forms a complex with CD14 and then with TLR-4 Signup and view all the answers

What role does NF-kB play in the immune response mechanism described?

It activates transcription of inflammatory cytokines Signup and view all the answers

What does the innate immune system's function primarily involve?

Attacking pathogens regardless of their identity Signup and view all the answers

Which of the following organs are considered the most important lymphoid organs?

Bone marrow and thymus Signup and view all the answers

What is the process called when cells migrate between blood and lymphatic capillaries?

Extravasation Signup and view all the answers

Which cytokine is NOT mentioned as being produced in response to TLR-4 activation?

IL-10 Signup and view all the answers

Which immune response is described as being triggered by specific pathogens?

Adaptive immunity Signup and view all the answers

What was Louis Pasteur's significant contribution to microbiology?

He disproved spontaneous generation and introduced pasteurization. Signup and view all the answers

Which of the following diseases was NOT developed into a vaccine by Louis Pasteur?

Tuberculosis Signup and view all the answers

What are Koch's Postulates primarily used for?

To prove the existence of infectious diseases caused by microbes. Signup and view all the answers

Which of these methods is involved in ribosomal RNA gene sequencing?

Amplification of rRNA using PCR. Signup and view all the answers

Which statement about cell size and metabolism is correct?

Smaller cells have higher metabolism rates. Signup and view all the answers

What do hyperthermophiles thrive in?

Temperatures above 80 °C. Signup and view all the answers

Which domains of organisms are included in the phylogenetic tree?

Bacteria, Archaea, and Eukarya. Signup and view all the answers

What is the primary measurement unit for microorganisms?

Micrometers (µm) Signup and view all the answers

What distinguishes prokaryotic chromosomes from eukaryotic chromosomes?

Prokaryotic chromosomes are located in the nucleoid, while eukaryotic are located in the nucleus. Signup and view all the answers

Which of the following characteristics is NOT typical of prokaryotic cells?

Presence of a nucleus. Signup and view all the answers

Which bacteria would retain the blue color after the Gram staining process?

Bacteria with thick peptidoglycan layers. Signup and view all the answers

What is the primary site of respiration in prokaryotic cells?

Cell membrane. Signup and view all the answers

Which of the following statements about ribosomes is correct?

Prokaryotic ribosomes are composed of 70S, while eukaryotic ribosomes are composed of 80S. Signup and view all the answers

What type of locomotion is characteristic of prokaryotic cells?

Rotating flagella. Signup and view all the answers

What is the effect of the iodine solution in the Gram staining process?

It fixes the blue dye in all bacterial cells. Signup and view all the answers

Which of the following structures is typically absent in prokaryotic cells?

Mitochondria. Signup and view all the answers

Study Notes

Microbiology Study Notes

Microbiology is the scientific study of microorganisms, being unicellular, multicellular, or acellular. It includes virology, bacteriology, protistology, mycology, immunology, and parasitology.
Microbes are everywhere, originating all forms of life, and comprising the majority of biomass on Earth. They exist virtually everywhere where water is available, often under the Earth's surface.
Microbes are essential to the food chain and affect the climate. They also are symbiotic with animals, humans, and other microbes; simply essential for life.
Pathogenic microorganisms significantly affected human populations historically, leading to death in 1900. While they remain important, infectious disease is less significant now.
Infectious diseases, accidents, perinatal and maternal diseases and others are significant causes of death in both developed and developing countries. Infectious disease is a leading cause of death in developing countries.

Milestones of Microbiology

Antoni van Leeuwenhoek (1632-1723): A natural philosopher, he made microscopes and observed bacteria.
Louis Pasteur (1822-1895): Demonstrated infectious diseases are caused by microbes (Swan-necked Flask Experiment), developed pasteurization, and vaccines for diseases like anthrax and rabies.
Robert Koch (1843-1910): Developed postulates for proving cause and effect in infectious diseases. Discovered that bacteria can cause diseases like anthrax, tuberculosis, and cholera, and received a Nobel Prize.

The Diversity of Microorganisms

Three domains of organisms exist: Bacteria, Archaea, and Eukarya.
Organisms are grouped by phylogenic tree.
Hyperthermophiles are prokaryotes that reach their optimal growth at a temperature of 80°C or higher.
Ribosomal RNA (rRNA) gene sequencing is used to create a phylogenetic tree and understand relationships between organisms.

Size of Microorganisms

Microorganisms range in size from 0.2 μm to 50 μm.
The ratio of surface area to volume in cells decreases as the size of the cell increases and this directly affects the cell's metabolism.

Properties of all cells

All cells have a cytoplasmic membrane, cytoplasm, a genome made of DNA, and ribosomes.
All cells use encoded information in DNA to make RNA and protein.
All cells take up nutrients, transform them, conserve energy and expel wastes.
2 major categories of metabolism: catabolism and anabolism.
All cells undergo growth using information to convert nutrients into new cells.
Cells evolve through mutations in DNA.

Properties of Some Cells

Some cells can form new structures such as spores.
Cells interact with each other via chemical messengers.
Some cells are capable of self-propulsion.
Cells exchange genes by various mechanisms.

Gram Staining

Gram-positive bacteria have a thick peptidoglycan layer and no outer membrane.
Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane.

Cell Wall Structure

The backbone of peptidoglycan is formed from N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM).
Peptidoglycan provides protection and shape to bacteria.
Penicillin-binding proteins (PBPs) catalyze the polymerization of NAG and NAM and crosslinking of peptide bridges, interrupting peptidoglycan synthesis.
Lysozyme also breaks down these connections.
Archaea have pseudopeptidoglycan and S-layers, similar in structure to peptidoglycan, but using N-acetyltalosaminuronic acid instead of muramic acid.

Outer Membrane of Gram-Negative Bacteria

Gram-negative bacteria have an outer membrane that contains lipopolysaccharides.
Ca2+ ions are required to maintain the stability of the lipopolysaccharide layer.

Cytoplasmic Membrane

The cytoplasmic membrane is a selectively permeable membrane, important for maintaining the cell's environment.
This membrane is a fluid mosaic model consisting mostly of phospholipids.
The composition of the membrane is homeovcous, adapting to environmental conditions to preserve fluidity.
There are 3 major mechanisms for moving molecules: passive diffusion for small molecules and water; facilitated diffusion, and active transport.

Surface Structures: Flagella, Fimbriae and Capsules

Flagella enable movement, distributed over the whole surface (peritrichous), or are located at a single pole (monotrichous), or at both (amphitrichous).
Fimbriae are used to attach to the surfaces of host cells, aiding in colonization and potential infection.
Capsules are polysaccharide structures that protect bacteria from phagocytosis.

Endospores

Some gram-positive bacteria can form endospores, which enables them to survive harsh environments and conditions.
This protects the bacterium from environmental influences.

The Hallmarks of Cellular Life

For cellular self-replication sufficient energy and genetic material must be provided or replicated beforehand.
Gene expression (transcription and translation) produces proteins for cellular function.

Information Storage in DNA and RNA

DNA is a double helix (anti-parallel), composed of deoxyribose, phosphate residue, and bases.
RNA is a single strand, composed of ribose, and phosphate residue, and bases.
DNA & RNA bases differ (uracil instead of thymine).
The sequence of nucleotides in mRNA translates to proteins.

DNA Replication

DNA is replicated in the 5' to 3' direction.
Multiple enzymes are involved in the process: DNA polymerase, DNA ligase.

Transcription (DNA → RNA)

RNA synthesis occurs at specific sites (promoters) on DNA.
The sigma factor is required for the polymerase to find promoters.
The RNA polymerase moves down the DNA strand, separating the double helix temporarily.
Transcription proceeds until a termination site is reached, releasing the mRNA and the polymerase.

Translation (RNA → Protein)

Ribosomes translate RNA into proteins.
Three nucleotides code for one amino acid, read by the tRNA.
The sequence of nucleotides is read in consecutive groups of three.

Amino Acids: Building Blocks of Proteins

20 amino acids are common to proteins.
Amino acids have an amino group, a carboxyl group and a characteristic side group ("R").
These groups are divided into 4 categories: ionizable: acidic, ionizable: basic, nonionizable polar, and nonpolar.

Bacterial Growth: Binary Fission

Bacteria reproduce by binary fission.
This involves DNA replication, cell elongation, septum formation, and the separation of the two daughter cells.
Bacterial growth is characterized by distinct phases: lag phase, log phase, stationary phase, and death phase.

Abiotic Parameters Affecting Bacterial Growth

Temperature affects enzymatic reactions.
Osmolarity affects water balance.
pH affects enzymatic activity.
Oxygen affects some cultures.
Water activity affects microbial growth.

Microbial Growth in Different Environments

Bacteria can grow at varied temperatures; thermophiles grow at higher temperatures, mesophiles at moderate temperatures, and psychrophiles at lower temperatures.
Factors that influence survival are enzyme stability, membrane fluidity, and the structure of the protein.

pH and Growth

Most bacteria can grow over a wide pH range, but pHi (intracellular pH) tends to remain near neutral.
They do this using enzyme-catalyzed reactions (consumption of protons/acids).
Cells alter lipid composition of the cytoplasmic membrane to reduce permeability to protons during extreme pH conditions.

Osmolarity

Bacteria alter their internal solute concentration or pump substances into cells to maintain a consistent internal environment when exposed to high or low external solute concentrations.
Compatible solutes are water-soluble sugars, alcohols, and amino acid derivatives that maintain osmotic balance.

Water activity

Bacteria require relatively high water activity to thrive.
Water activity is measured as Aw, which may vary from 0 to 1.
Aw values below 0.95 are unfavourable for many bacteria.

Methods of Preventing Microbial Growth

Heat sterilization (autoclave)
Heat (pasteurization)
Ionizing radiation
Filtration
Chemical agents (disinfectants)

Chemical Growth Control: Antibiotics

Antibiotics interfere with bacterial growth through various pathways depending on their type.
Antibiotics can be bacteriostatic, bacteriocidal, or bacteriolytic, by affecting protein synthesis, cell wall synthesis, folate synthesis, nucleic acid synthesis and cell membrane.

Resistance to Antibiotics

Many pathogens are becoming resistant; preventing and treating infections is becoming an increasing challenge.
Modifications to the bacterial cells/structures, like the production of efflux pumps, often lead to resistance.

Mechanisms of Antimicrobial Drug Resistance

Efflux pumps, inactivation, target modification, and target bypass are some resistance mechanisms bacteria can use.

Nutritional Requirements for Microbial Growth

Required nutrients include carbon, hydrogen, oxygen, nitrogen, phosphorus, sulfur, potassium, magnesium, sodium, calcium, iron, as well as trace-elements and vitamins.

Culture Media for Bacteria

Defined media is specifically composed media for a specific strain, composed of specific components and chemical quantities.
Complex media contain various macro- and micronutrients that enable various organisms to grow.

Cellular Respiration: The Citric Acid Cycle and Electron Transport Chain

Respiration pathways, such as aerobic respiration, produce ATP.
The citric acid cycle breaks down acetyl-CoA, producing energy.
The energy from the electron transport chain is used to generate a proton gradient that drives ATP synthesis.

Types of Bacterial Metabolism

Chemoorganotrophs: use organic compounds for energy.
Chemolithotrophs: use inorganic compounds for energy.
Phototrophs: use light for energy.
Heterotrophs: use organic compounds as carbon sources.
Autotrophs: use carbon dioxide to produce organic compounds.

Chemolithotrophic Metabolism

Chemolithotrophs use oxidation of inorganic compounds to produce energy and synthesize cellular components.
Several types of chemolithotrophic metabolism exist and use reactions where e.g., ammonia or nitrite are oxidized to produce energy for the cell.

Phototrophic Metabolism

Phototrophs use light as a source of energy to produce ATP.
Photosynthesis can produce oxygen as a byproduct (oxygenic photosynthesis) or not (anoxygenic photosynthesis).
Several important types of phototrophs include cyanobacteria, purple sulfur bacteria, and purple nonsulfur bacteria.

Regulation of Gene Expression

The product of a gene may be an enzyme or other protein directly involved in cell function.
Synthesis of gene product can be initiated, regulated or inhibited through transcriptional and/or translational control.

Mechanisms of Gene Regulation: Operons

Operons are clusters of genes that are transcribed together; coordinated regulation of expression.
Repressors prevent transcription, while activators promote it.

Regulation of Gene Expression Mechanisms

small RNA molecules and riboswitches regulate translation.
Co-transcriptional and co-translational processing of RNA influences function.

Post-Translational Regulation: Feedback Inhibition

Synthesis of polypeptide chains and subsequent modifications may be controlled and regulated at various points.
Enzymes can be inhibited, especially the initial enzyme in a sequential conversion pathway, by end product through allosteric feedback inhibition.
Allosteric feedback inhibition prevents the production of excess product.

Post-Translational Regulation- Covalent Modification

Covalent modification, such as the addition or removal of chemical groups to proteins (e.g., adenylation).
This can change their shape and functionality
Regulation of enzyme activity often involves covalent modification

Viral Replication

The basic viral replication cycle involves adsorption, penetration, uncoating, synthesis, maturation, and release (sometimes called assembly).

The Diversity of Viral Genomes

Viral genomes can be DNA or RNA, and can be single-stranded (ss) or double-stranded (ds).
Viral genomes are categorized into different groups.

Bacterial Phage Receptors

Many bacteriophages have receptors on their surface where they may adhere to bacterial cells to initiate infection.
These receptors may be proteins, polysaccharides, etc..

Bacteriophages Replication Cycle

Several methods, such as lytic and lysogenic cycles exist for viral replication.
The lytic cycle results in the lysis and destruction of the host cell while providing new infectious phage virions compared to the lysogenic cycle, where the phage DNA integrates into the host genome, without immediately destroying it.
Some key viral components are present in phage replication, such as genomes, endolysins.

Timeline of Events During Lytic Phage Infection

Early viral proteins are produced to initiate gene expression and genomic replication (e.g., nucleases, DNA polymerase, and other phage-specific sigma factors).
Late viral proteins are produced for virion assembly and release (e.g., phage structural proteins and lysozyme).

Phage Lambda: A Temperate Phage

A Temperate Phage establishes lysogeny by integrating its DNA into the host genome; producing prophages which can be excised at a later time to establish a lytic cycle.
Regulatory proteins (Cro, ci) determine whether a lytic or lysogenic cycle takes place
The process involves integration events, excision (cleavage of prophage DNA from the host chromosome), DNA replication.

Phi-X174: Phage with a Single-Stranded DNA Genome

Phi-X174's small genome features a single-stranded DNA genome that is partially duplicated via a self-replication mechanism and provides an advantage in DNA sequencing.

Phage M13: A Filamentous Phage

Phage M13 is a filamentous phage which does not kill the host cell; it replicates and leaves host cells via exocytosis.
Bacteria may use M13, and other similar phages, for information exchange.

Phage MS2: A Small (+) RNA Phage

The phage MS2's genome is a single-stranded (+) RNA capable of being translated into proteins without a DNA intermediate.

The Diversity of Animal Viruses

Viruses are characterized by their highly diverse structures and relative sizes, and vary by genome type.

The Lytic Human Herpesvirus Life Cycle

Binding, entry (fusion or endocytosis), nuclear transport, nuclear entry, gene expression, DNA replication, packaging, and egress are the key steps.

Poliovirus

The Poliovirus has a single-stranded (+)RNA genome, and is part of the Picornaviridae family.
The Poliovirus has a protective capsid that protects against environmental stresses.

Structure and Function of a Retrovirus

Retroviruses, such as HIV, have an RNA genome.
This RNA genome is transcribed into DNA (with reverse transcriptase).

The Lifecycle of Human Retroviruses

Entry via specific receptors (for cells like CD4 /CCR5/CXCR4) on the plasma membrane.
Then the viral genome is transported through nuclear pores.
Reverse transcription produces viral DNA, which is integrated into the host genome to produce proviral DNA.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2)

Coronaviruses belong to the family of enveloped (+)RNA Viruses.
Their genomes are extremely large.
The virus infects cells by binding to receptors like ACE2.
The virus can use an endocytosis pathway.

Viroids

Viroids are small, single-stranded circular RNA molecules
Viroids do not code for proteins and depend on the host enzymes for replication and regulation of expression, to cause plant diseases.

Prions

Prions are misfolded and aggregated proteins known as prions, which are uniquely infectious and very resistant to usual measures.
Prions cause rapidly progressive, incurable neurodegenerative disorders.
They produce abnormally folded prion protein (PrPSc) which catalyzes the refolding of normal prion protein (PrPc) into the PrPSc form.

The Microbiome

The microbiome is the collection of all microorganisms (bacteria, fungi, virus) that live in or on a multicellular organism.
Microbial populations play a role in human health (including synthesis of vitamins, digestion, amino acid production) and health disorders.

Biochemical/Metabolic Contributions of Intestinal Microorganisms

Intestinal bacteria synthesize many vitamins and amino acids, fermenting sugars lead to gas production, and produce various short-chain organic acids.

Fermentation in the Colon of Lean and Obese Mice and Transfer of an Obese Condition by Fecal Transplant

Obese mice contain more firmicutes (bacteria), compared to lean mice, that produce more H2 during fermentation.
Volatile fatty acids (VFAs) are produced during fermentation.

Physical, Chemical, and Anatomical Barriers Against Infection

Barriers exist and protect against pathogen invasion in the body (chemical, mechanical, epithelial barriers and the microbiome).
These barriers stop entry of pathogens.

The First Step of Infection: Bacterial Adherence

Adherence is the initial step of bacterial infection.
Bacterial structures (like capsules, fimbriae, flagella and pili) assist in adhering to the host cell.
Biofilms may aid in establishment of bacteria.

Enzyme Virulence Factors of Some Gram-Positive Bacterial Pathogens

The activity of some enzymes, as virulence factors (example hyaluronidase, coagulase and streptokinase), may destroy tissues (affect host cells), and break down tissues (affect hosts), leading to bacterial spread in the host.

Pathogenicity Islands and Plasmids in Salmonella

Pathogens like Salmonella have various virulence factors in various islands or plasmids.
These structures contain genes encoding factors for pathogenicity.

Some Exotoxins and Cytotoxins

Exotoxins and cytotoxins are protein toxins secreted by bacteria.
Superantigens trigger a massive immune response, unlike other exotoxins, affecting whole populations of T-cells.

AB-Toxins

AB toxins consist of two parts: A unit (toxic) and B unit (binding).
Diphtheria toxin exemplifies this class, where toxin A catalyzes ADP ribosylation and inactivates elongation factor affecting eukaryotic translation, resulting in cell death.

Clostridium Botulinum Toxin

C. botulinum produces a potent neurotoxin,
This toxin blocks acetylcholine release at neuromuscular junctions prevents muscle contraction.

The Cholera Toxin Excreted by Vibrio Cholerae

Vibrio cholerae is an anaerobic comma-shaped bacterium commonly found in brackish or saltwater
It produces cholera toxin (CT) that results in severe diarrhea.

Cytotoxins (Cytolytic Toxins)- The Staphylococcal a-Toxin

The a-toxin is often secreted by Staphylococcus aureus.
Staphylococcal a-toxin is a pore-forming cytotoxin creating transmembrane pores into host cells and causing cell lysis.

Exotoxins vs. Endotoxins

Exotoxins are secreted proteins, and are highly toxic in very small quantities, often causing specific reactions.
Endotoxins are LPS components that are part of the outer membrane of gram-negative bacteria, causing fever and general reactions even in large amounts.

Basics of Immunology

The immune system has two-pronged defenses: innate and adaptive.
Innate immunity acts rapidly and generally against a broad spectrum of pathogens; it doesn't have immunological memory.
Adaptive immunity involves more specific targeting and has immunological memory, enabling quicker future responses to encountered pathogens.

The Blood and Lymphatic Systems

The blood and lymphatic systems serve as the transport and circulatory systems for cells and proteins within the body.
Major blood components include erythrocytes (red blood cells), leukocytes (white blood cells), lymphocytes, and granulocytes/monocytes.

Microbial Invasion and the Innate Immune Response

Infection leads to microbial invasion from tissues.
Pathogens are recognized via the pathogen-associated molecular patterns (PAMPs), allowing the immune response pathway to be triggered.
Phagocytes (macrophages, neutrophils) are attracted and activated using chemokines and phagocytose invading pathogens.
Cytokines are released to direct and regulate the innate immune response.

Signal Transduction in Innate Immunity

Signal transduction pathways are frequently generated by PAMP binding to pattern recognition receptors (PRRs) on the surface of phagocytes.
This sets off a series of chemical modifications to proteins which will ultimately lead to a response, like a quicker or more controlled immune response by phagocytes.

Phagocytosis

Phagocytosis is the biological process of engulfing and eliminating pathogens (like bacteria) by phagocytes (immune cells)..
Toxic oxygen compounds are created (e.g., hydrogen peroxide, hydroxyl radical, hypochlorous acid, superoxide anion, singlet oxygen, nitric oxide).
Toxic compounds are used to kill pathogens.

Inflammation and Fever

The release of inflammatory cytokines (IL-1, IL-6, TNF-α) induces fever.
These chemicals cause the brain's temperature control center to produce prostaglandins, which increase body temperature.

Adaptive Immunity

Adaptive immunity includes T cells and B cells.
T cells are a type of immune cell involved in cell-mediated immunity, while B cells produce antibodies.

Antigen Presentation

MHC (major histocompatibility) complexes are integral proteins utilized in adaptive immune responses to present antigens to their corresponding receptors in order to activate an adaptive response.
MHCs exist in 2 forms (I and II) that present different sources, cellular proteins or exogenous proteins, and present them to different types of T cell receptors.

T-Helper Cell Subsets

Th cells (T helper) aid in antibody immunity and cell-mediated immunity by producing various cytokines.
There are subsets of Th cells, such as Th1, Th2, and Th17, each with specific functions.

T-Helper Cell Subsets and T-cell Selection and Clonal Deletion

Immune cells (T cells) are selected and matured, allowing them to respond to infection and not to their own body tissues (self-tolerance).
This process is necessary to prevent autoimmune responses, where immune cells attack the host's own tissues.

B Cell Clonal Selection and Expansion

B cells, which recognize and respond to specific antigens by producing antibodies, are selected and expanded to generate clones with the same antigen-specific antibody, via clonal selection.
Antibodies binding to antigens leads to continued proliferation of clones of the responsive B cells.

Properties of Human Immunoglobulins

Antibodies (Immunoglobulins) are Y-shaped proteins.
They have variable regions that bind to specific antigens and constant regions that mediate interactions with other parts of the immune system.
There are different classes, with differing activities in the body.

Active and Passive Immunity

Active immunity is the immunity that an organism develops during an infection and results in immunological memory responses that can be recalled for future exposure.
Passive immunity is the form of immunity received or transferred via antibodies.

Immunoglobulin Gene Rearrangement in Human B Cells

Immunoglobulins have genes that rearrange in various ways to generate a large diversity for antigen-recognition receptors and to give each B cell unique specificity.
This diversity is necessary to generate a variety of immune responses to combat various pathogens and to prevent autoimmune responses.

Antibodies: Functions and Role

Antibodies bind to specific antigens.
They can block pathogen interactions with host cells, promote phagocytosis, and neutralize toxins.

Complement Proteins and Complement Activation

The complement system is a group of innate immune proteins that enhance the overall immune system's ability to respond to pathogens.
Classical, lectin, and alternative pathways activate complement through the combination and splitting reaction of various proteins leading to lysis and inflammation.

Epidemiology

Epidemiology studies diseases patterns, causes, and effects in entire populations.
Endemic, epidemic, and pandemic disease are characterized by the distribution of disease prevalence.
Key parameters in disease transmission to consider include the type of contact, mode, and route, for example, direct or indirect contact via fomites, droplets, vectors, carriers or other vehicles like contaminated water or food.

Herd Immunity

Herd immunity is the immunity of a human population to an infectious agent, due to a large proportion of immune individuals; those individuals with immunity protect the susceptible.
Herd immunity is a critical aspect of disease prevention and control.

Countermeasures

Countermeasures are methods to reduce or prevent infections.
Filters, chlorination of water, and vaccines are examples.
Herd immunity is maintained by widespread vaccination.

The T7 Expression System

The T7 expression system is a bacterial expression system allowing the controlled and rapid production of a specific protein and is designed for quick protein expression, and manipulation.

Site-Directed Mutagenesis & Gene Disruption

Using this technique, one can deliberately introduce a specific change in DNA sequence (e.g., a mutation), generating the desired product quickly and efficiently.
This allows for studying the influence of various mutations and identifying specific functional components of a gene/protein.

Recombinant DNA Technology: Synthesis of Insulin

Insulin can be synthesised via this technique utilizing prokaryotes (e.g. E coli) or eukaryotes (e.g. yeast).
This method allows for the production of complex proteins, from a foreign gene.

Production of Transgenic Plants and Viruses

Plants and animal virus genes can be inserted using binary vectors inside specific tissues.
These methods enable generating plants and animal cells that expressed the gene of interest after the insertion process.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on key concepts in molecular biology, focusing on transcription and translation processes. This quiz covers components like RNA polymerase, the function of tRNA, and the role of ppGpp during amino acid starvation in prokaryotes. Challenge yourself with questions that address the intricacies of the replisome and ribosomal subunits.