1. Explain the mechanisms by which the immune system identifies and
combats pathogens in the human body. How does the concept of immunological
memory aid in the body’s defense against infections?
Answer:
The immune system protects the body from pathogens (bacteria, viruses, fungi,
etc.) using a variety of mechanisms.
- Innate Immunity: The first line of defense is the innate immune
system, which includes physical barriers like the skin and mucous membranes,
along with nonspecific immune cells (e.g., phagocytes) and chemicals (e.g.,
lysozyme). These recognize and attack pathogens in a broad and nonspecific
manner.
- Adaptive Immunity: If the innate system cannot eliminate the
pathogens, the adaptive immune system is activated. It involves T
lymphocytes (T-cells) that help in cell-mediated immunity, and
B lymphocytes (B-cells) that produce antibodies, providing humoral
immunity. B-cells recognize specific antigens on pathogens and produce
antibodies that bind to the pathogen, marking it for destruction.
- Immunological Memory: Once the adaptive immune system has
responded to a pathogen, it creates memory cells. These are
long-lived cells that "remember" the specific pathogen. If the same pathogen
enters the body again, the memory cells activate a quicker and stronger immune
response. This is the basis of vaccination and immunity,
ensuring faster recovery upon reinfection.
2. Discuss the role of vaccines in preventing diseases and explain how
they contribute to herd immunity.
Answer:
Vaccines are biological preparations that provide immunity to specific diseases
by stimulating the immune system without causing the disease itself. Vaccines
often contain antigens derived from the pathogen (such as
weakened or inactivated viruses or bacteria) that stimulate the immune response.
- How Vaccines Work: When a person is vaccinated, their immune
system mounts a response to the antigens in the vaccine, producing
memory cells. These cells "remember" the pathogen, ensuring a rapid
response if the person is exposed to the disease-causing agent in the future.
- Herd Immunity: Vaccination of a large portion of the population
reduces the spread of infectious diseases, protecting even those who are
unvaccinated or have weakened immune systems. This is called herd
immunity. When a significant proportion of the population is immune,
the pathogen has fewer opportunities to spread, leading to a decrease in disease
transmission.
3. Describe the different types of allergies and explain the
immunological basis behind the hypersensitivity reactions associated with them.
Answer:
Allergies occur when the immune system responds inappropriately to harmless
substances (allergens), triggering hypersensitivity reactions.
There are four main types of hypersensitivity reactions:
- Type I (Immediate Hypersensitivity): This is mediated by
IgE antibodies. Upon initial exposure to an allergen (like
pollen or dust), the body produces IgE antibodies, which bind to mast
cells and basophils. Upon subsequent exposure, the
allergen binds to the IgE, causing the release of histamines
and other inflammatory mediators, leading to symptoms like itching, swelling,
and anaphylaxis.
- Type II (Cytotoxic Hypersensitivity): In this type, IgG or IgM
antibodies bind to the antigen on the surface of cells, leading to cell
destruction through the activation of the complement system or phagocytosis.
Conditions like hemolytic anemia can result from this type of
reaction.
- Type III (Immune Complex Hypersensitivity): This involves the
formation of immune complexes (antigen-antibody complexes) that
deposit in tissues, triggering inflammation and damage. An example of this is
rheumatoid arthritis.
- Type IV (Delayed-Type Hypersensitivity): This type is mediated
by T-cells, not antibodies. It involves the activation of
T-helper cells, which release cytokines that recruit macrophages to the site of
infection, causing inflammation. Tuberculosis testing (Tine or
Mantoux test) is based on this type of hypersensitivity.
4. Explain the concept of immunodeficiency disorders. Compare primary
and secondary immunodeficiency, with examples.
Answer:
Immunodeficiency disorders occur when the immune system fails to respond
effectively to infections.
- Primary Immunodeficiency: This is usually genetic, meaning it
is present from birth. The most common example is severe combined
immunodeficiency (SCID), where both T-cells and B-cells are absent or
dysfunctional, severely impairing the immune response. Another example is
DiGeorge syndrome, where there is a defect in T-cell
development due to a chromosomal deletion.
- Secondary Immunodeficiency: This type occurs due to external
factors, such as infections (e.g., HIV/AIDS) or malnutrition.
HIV attacks the CD4+ T-cells, weakening the immune system and
making the body vulnerable to opportunistic infections.
In both cases, the body becomes more susceptible to infections, and secondary
infections can lead to severe complications.
5. Discuss the mechanism of action of antibiotics and the issue of
antibiotic resistance.
Answer:
Antibiotics are chemicals that inhibit the growth of bacteria or kill them by
targeting essential bacterial processes.
- Mechanism of Action:
- Inhibition of cell wall synthesis: Penicillins and
cephalosporins prevent bacterial cell wall formation, leading to cell lysis.
- Inhibition of protein synthesis: Tetracyclines and
aminoglycosides bind to bacterial ribosomes and prevent protein synthesis,
hindering bacterial growth.
- Inhibition of nucleic acid synthesis: Drugs like
quinolones inhibit DNA replication, preventing bacterial cell division.
- Antibiotic Resistance:
The overuse and misuse of antibiotics have led to the development of
antibiotic-resistant bacteria. This occurs when bacteria mutate to
survive antibiotic treatment, rendering standard antibiotics ineffective.
Examples include methicillin-resistant Staphylococcus aureus (MRSA)
and multi-drug-resistant tuberculosis (MDR-TB). Resistance
mechanisms include:
- Enzyme production: Bacteria may produce enzymes (e.g.,
β-lactamase) that break down antibiotics.
- Efflux pumps: Bacteria can pump antibiotics out of their cells,
reducing their effectiveness.
- Alteration of target sites: Bacteria may modify the target site
of the antibiotic, making it ineffective.
6. Describe the pathophysiology of cancer and explain how abnormal cell
division leads to tumor formation.
Answer:
Cancer is a disease characterized by uncontrolled cell division and the spread
of abnormal cells throughout the body.
- Abnormal Cell Division: Cancer begins when genetic mutations
occur in the DNA of cells, causing them to lose the normal
regulatory mechanisms that control the cell cycle. Normally, cell division is
tightly regulated by tumor suppressor genes (e.g., p53) and
oncogenes (e.g., RAS).
- Tumor Suppressor Genes: These genes inhibit cell growth and
promote apoptosis (cell death) if the cell is damaged. Mutations in these genes
may lead to uncontrolled division.
- Oncogenes: These genes promote cell division. When mutated,
they can become oncogenes, leading to excessive cell division.
- Tumor Formation: These uncontrolled cells form a tumor.
Tumors can be classified as benign (non-cancerous) or malignant (cancerous).
Malignant tumors invade surrounding tissues and can spread to distant sites in
the body through a process called metastasis.
7. Discuss the role of lifestyle factors such as diet, exercise, and
stress in the development of diseases.
Answer:
Lifestyle factors play a significant role in both the prevention and development
of diseases.
- Diet: A poor diet, rich in processed foods, sugars, and fats,
can lead to obesity, diabetes, and
cardiovascular diseases. Conversely, a balanced diet with adequate
fiber, antioxidants, and micronutrients can help maintain optimal health and
prevent chronic diseases.
- Exercise: Regular physical activity helps maintain a healthy
weight, improves cardiovascular health, and reduces the risk of
diseases like hypertension, diabetes, and even
cancer. Exercise also boosts the immune system and can reduce
stress.
- Stress: Chronic stress leads to the continuous release of
stress hormones like cortisol, which can suppress immune
function, increase inflammation, and contribute to conditions like heart
disease, digestive issues, and mental health
disorders (e.g., anxiety, depression).
- Smoking and Alcohol Use: These lifestyle choices increase the
risk of lung cancer, liver disease,
heart disease, and other conditions. Smoking can damage the lungs,
while excessive alcohol consumption can lead to liver damage.
8. Explain the concept of zoonotic diseases and how they can be
transmitted from animals to humans. Provide examples.
Answer:
Zoonotic diseases are diseases that are transmitted from animals to humans. They
can be caused by bacteria, viruses, parasites, or fungi.
- Transmission: Zoonotic diseases can spread through direct
contact with infected animals or their bodily fluids (e.g., saliva, urine,
feces). They can also be transmitted through vectors like mosquitoes
or ticks, or by consuming contaminated animal products.
- Examples:
- Rabies: A viral infection transmitted through the bite of an
infected animal (usually dogs).
- Avian Influenza (Bird Flu): Caused by the H5N1 virus,
this can be transmitted through contact with infected birds or their droppings.
- Plague: Caused by the bacterium Yersinia pestis,
often spread by fleas from rodents.
- Malaria: Caused by Plasmodium parasites and
transmitted through mosquito bites.
9. Discuss the role of biotechnology in the production of vaccines and
diagnostic tools.
Answer:
Biotechnology has revolutionized the development of vaccines and diagnostic
tools, providing safer, more efficient, and rapid solutions.
- Vaccine Production:
- Recombinant DNA Technology: This technique allows scientists to
isolate and modify the genes responsible for producing antigens in pathogens,
creating recombinant vaccines.
- Subunit Vaccines: These vaccines use only a portion of the
pathogen (e.g., a protein) to stimulate an immune response without causing
disease.
- DNA and mRNA Vaccines: These vaccines involve introducing DNA
or RNA into the body, instructing cells to produce antigens that trigger an
immune response. The COVID-19 vaccines (Pfizer, Moderna) are
examples of mRNA vaccines.
- Diagnostic Tools:
- Polymerase Chain Reaction (PCR): PCR is used to amplify and
analyze specific segments of DNA, enabling the detection of pathogens.
- ELISA (Enzyme-Linked Immunosorbent Assay): This test detects
the presence of specific antibodies or antigens in a patient's blood, helping
diagnose infections like HIV.
10. Discuss the genetic basis of sickle cell anemia and how it affects
the human body.
Answer:
Sickle cell anemia is a genetic disorder caused by a mutation in the
hemoglobin gene, leading to the production of sickle-shaped red
blood cells.
- Genetic Mutation: The mutation occurs in the gene encoding
hemoglobin A (HbA), where adenine is replaced by thymine at the
sixth position in the beta-globin chain. This results in the formation of
hemoglobin S (HbS), which polymerizes under low oxygen
conditions, causing red blood cells to adopt a sickle shape.
- Impact on the Body:
- Impaired Oxygen Transport: Sickle-shaped red blood cells have
reduced flexibility and cannot efficiently carry oxygen.
- Blockage of Blood Flow: These abnormally shaped cells can clump
together, blocking blood vessels, leading to pain, organ damage, and increased
risk of infection.
- Anemia: The sickle cells are fragile and break down
prematurely, leading to a shortage of red blood cells (anemia).
11. Explain the concept of cancer immunotherapy and compare it with
traditional cancer treatments like chemotherapy and radiation therapy.
Answer: Cancer immunotherapy is a treatment strategy that
utilizes the body’s immune system to fight cancer. Unlike traditional treatments
like chemotherapy and radiation therapy, which target rapidly dividing cells
(both cancerous and healthy), immunotherapy specifically enhances the immune
system’s ability to recognize and attack cancer cells.
- Mechanisms of Immunotherapy:
- Checkpoint Inhibitors: These drugs block immune checkpoints
(such as PD-1 and CTLA-4) that prevent T-cells
from attacking cancer cells.
- Monoclonal Antibodies: These antibodies are engineered to
target specific cancer cell antigens, marking the cancer cells for destruction
by the immune system.
- CAR-T Cell Therapy: Involves modifying a patient’s T-cells to
better recognize and attack cancer cells.
- Comparison with Traditional Treatments:
- Chemotherapy and radiation therapy are
nonspecific treatments that kill both cancerous and healthy cells, leading to
side effects like hair loss, nausea, and immune suppression.
- Immunotherapy, while often more targeted, can lead to immune-related side
effects, such as inflammation of healthy tissues (e.g., colitis or hepatitis),
but it is less toxic to normal cells and can provide long-lasting protection
through the development of immunological memory.
- Immunotherapy is also more effective for cancers that evade the
immune system, such as melanoma and non-small-cell lung cancer, and has shown
promise in providing durable remissions.
12. How does the human body’s response to stress affect the development
of chronic diseases?
Answer: Stress activates the
hypothalamic-pituitary-adrenal (HPA) axis and autonomic nervous system,
leading to the release of stress hormones like cortisol and
adrenaline. While acute stress can be protective, chronic
stress has been linked to various chronic diseases.
- Chronic Activation of Stress Pathways:
- Long-term stress leads to prolonged cortisol production, which can impair immune
function, increase blood pressure, and promote inflammation,
all of which are risk factors for conditions such as heart disease,
stroke, and diabetes.
- Chronic stress can also lead to metabolic imbalances, promoting obesity,
insulin resistance, and type 2 diabetes.
- Impact on Mental Health: Chronic stress can contribute to
mental health disorders, including depression and anxiety, by
altering brain function and reducing neurogenesis in regions like the
hippocampus.
- Behavioral Changes: Stress may lead to unhealthy behaviors,
such as smoking, overeating, or lack of exercise, further contributing to
disease development.
- Immune System Suppression: Elevated cortisol levels inhibit the
effectiveness of the immune system, making the body more susceptible to
infections and possibly delaying recovery from diseases.
13. Describe the pathophysiology of AIDS and explain how the HIV virus
damages the immune system.
Answer: Acquired Immunodeficiency Syndrome (AIDS) is caused by
the Human Immunodeficiency Virus (HIV), which primarily attacks
CD4+ T-cells, a type of white blood cell that plays a crucial
role in the immune response.
- HIV Infection Process:
- HIV targets CD4+ T-cells by binding to the CD4 receptor
and CCR5 or CXCR4 co-receptors on the cell surface. Once inside
the cell, the virus uses the host cell’s machinery to replicate and produce more
virus particles.
- Over time, the virus kills CD4+ T-cells, weakening the immune system and
reducing its ability to mount an effective response to infections and cancers.
- Progression to AIDS:
- The initial stage of HIV infection (acute retroviral syndrome) may present
flu-like symptoms, but over several years, the number of CD4+ T-cells
progressively declines.
- When the CD4+ count falls below a critical threshold (usually 200 cells per
microliter of blood), the immune system is severely compromised, leading to
AIDS.
- Opportunistic Infections: Due to a weakened immune system,
individuals with AIDS are highly susceptible to opportunistic infections
(e.g., tuberculosis, fungal infections) and certain cancers (e.g., Kaposi's
sarcoma).
14. Explain the mechanism by which malaria is transmitted and discuss
the life cycle of the Plasmodium parasite in both the human host and the
mosquito vector.
Answer: Malaria is caused by Plasmodium
parasites, which are transmitted to humans through the bite of infected
Anopheles mosquitoes.
- Transmission Process:
- When an infected mosquito bites a human, it injects sporozoites
(the infectious form of the parasite) into the bloodstream.
- These sporozoites travel to the liver, where they mature and reproduce.
- After multiplying in the liver, the parasites (now called merozoites)
enter the bloodstream and infect red blood cells, causing them to burst and
release more merozoites, which infect other red blood cells. This leads to the
symptoms of fever, chills, and anemia.
- Mosquito Life Cycle:
- When another mosquito bites an infected person, it ingests the gametocytes
(reproductive forms of the parasite).
- Inside the mosquito’s digestive tract, the gametocytes fuse and form
ookinetes, which invade the mosquito’s gut and mature into
oocysts.
- The oocysts release sporozoites, which travel to the mosquito’s salivary glands,
ready to infect the next human host.
15. Discuss the genetic basis and symptoms of phenylketonuria (PKU). How
is this metabolic disorder diagnosed and managed?
Answer: Phenylketonuria (PKU) is a genetic disorder
caused by mutations in the PAH gene, which encodes the enzyme
phenylalanine hydroxylase. This enzyme is responsible for
converting the amino acid phenylalanine into tyrosine.
- Genetic Basis:
- PKU is inherited in an autosomal recessive manner, meaning an
individual must inherit two copies of the mutated gene (one from each parent) to
develop the disorder.
- Symptoms:
- Phenylalanine builds up in the blood and brain, leading to
intellectual disability, developmental delay, seizures, and behavioral problems
if untreated.
- Diagnosis:
- PKU is typically diagnosed through the newborn screening test,
which measures phenylalanine levels in the blood shortly after birth.
- Management:
- The primary treatment is a phenylalanine-restricted diet, which
limits high-protein foods (such as meat, dairy, and nuts) to prevent
phenylalanine accumulation.
- Early diagnosis and dietary management can prevent intellectual disability and
allow affected individuals to lead normal lives.
16. Describe the role of human microbiota in maintaining health. How do
imbalances in the microbiota contribute to diseases?
Answer: The human microbiota consists of
trillions of microorganisms, including bacteria, viruses, fungi, and protozoa,
that reside primarily in the gut but are found throughout the body.
- Role in Health:
- Immune System Regulation: The microbiota helps educate the
immune system, ensuring appropriate immune responses.
- Nutrient Synthesis: Microbiota produce essential vitamins
(e.g., vitamin K, B vitamins) and help digest
complex carbohydrates.
- Pathogen Defense: Beneficial microbes compete with pathogenic
microorganisms for resources, helping to prevent infections.
- Imbalance and Disease (Dysbiosis):
- Dysbiosis, an imbalance in the microbiota, has been linked to various diseases,
including inflammatory bowel disease (IBD), obesity,
type 2 diabetes, and autoimmune disorders.
- Factors such as antibiotic use, poor diet, and stress can
disrupt the microbiota, reducing its protective functions and increasing
susceptibility to disease.
17. Explain the role of inflammation in the body’s immune response. How
does chronic inflammation contribute to diseases like arthritis and
cardiovascular diseases?
Answer: Inflammation is a protective response of the immune
system to infection, injury, or harmful stimuli. It involves the activation of
immune cells and the release of inflammatory mediators like cytokines
and prostaglandins.
- Acute Inflammation:
- In acute inflammation, immune cells such as neutrophils and
macrophages migrate to the site of infection or injury, where
they release substances that help fight infection and repair tissues.
- Chronic Inflammation:
- When inflammation persists over time, it becomes chronic and can damage healthy
tissues. Chronic inflammation is linked to diseases such as:
- Arthritis: Inflammatory cells attack the joints, causing pain,
stiffness, and swelling.
- Cardiovascular Diseases: Chronic inflammation of blood vessels
can lead to the development of atherosclerosis, where plaque
builds up and narrows the arteries, increasing the risk of heart attacks and
strokes.
18. Discuss the concept of autoimmune diseases and explain the
mechanisms that cause the immune system to attack the body’s own cells.
Answer: Autoimmune diseases occur when the immune system
mistakenly targets and attacks the body’s own cells and tissues, perceiving them
as foreign invaders.
- Mechanisms:
- Loss of Immune Tolerance: Normally, the immune system can
distinguish between self and non-self, but in autoimmune diseases, this
tolerance is lost.
- Molecular Mimicry: In some cases, pathogens have proteins
similar to those of the host, leading to the immune system attacking both the
pathogen and the host tissue.
- Failure of Regulatory T-cells: Regulatory T-cells (Tregs)
normally prevent autoimmunity by suppressing inappropriate immune responses. In
autoimmune diseases, Tregs may be ineffective.
- Examples of Autoimmune Diseases:
- Type 1 Diabetes: The immune system attacks insulin-producing
cells in the pancreas.
- Multiple Sclerosis: The immune system attacks the myelin sheath
of nerve cells in the brain and spinal cord.
- Rheumatoid Arthritis: The immune system attacks the joints,
leading to inflammation and damage.
19. Explain the process by which the human body develops immunological
memory after exposure to a pathogen. How is this concept applied in vaccination?
Answer: Immunological memory refers to the ability of the
immune system to remember a pathogen after an initial exposure and respond more
rapidly and effectively upon subsequent exposures.
- Development of Memory Cells:
- Upon exposure to a pathogen, the immune system activates B-cells
(which produce antibodies) and T-cells (which destroy infected
cells). Some of these cells become memory cells, which persist long after the
infection has cleared.
- Memory B-cells can quickly produce the appropriate antibodies
if the pathogen is encountered again, while memory T-cells can
recognize and kill infected cells more efficiently.
- Vaccination:
- Vaccination works by introducing a harmless form of a pathogen (e.g.,
inactivated virus, subunit, or mRNA) into the body. This stimulates the immune
system to produce an immune response and develop memory cells, without causing
disease.
- If the person encounters the actual pathogen later, the immune system can mount
a faster and more effective defense.
20. Explain the differences between active immunity and passive
immunity. Discuss how each type plays a role in protecting the human body
against diseases.
Answer:
- Active Immunity:
- Active immunity is generated when the immune system is exposed to a pathogen and
produces an immune response, including the activation of B-cells
and T-cells, leading to the production of antibodies and memory
cells. This form of immunity is typically long-lasting and is developed either
through natural infection or vaccination.
- Example: After recovering from an infection like measles, the
body’s immune system produces memory cells that provide immunity against future
infections by the same pathogen. Similarly, vaccines stimulate the immune system
to produce memory cells without causing the disease itself.
- Passive Immunity:
- Passive immunity is provided when antibodies or immune cells from an external
source are introduced into the body. It does not require the immune system to
produce its own response, and the immunity is temporary, typically lasting weeks
to months.
- Example: Antibodies passed from a mother to her child through
the placenta or breast milk provide passive immunity to the newborn.
Additionally, the administration of immunoglobulins or
monoclonal antibodies can provide passive immunity to individuals
exposed to certain diseases, such as in the case of rabies or
tetanus.
21. Discuss how antibiotic resistance develops and its impact on the
treatment of infectious diseases.
Answer: Antibiotic resistance occurs when bacteria evolve
mechanisms to resist the effects of drugs that previously killed them or
inhibited their growth.
- Mechanisms of Resistance:
- Mutation and Natural Selection: Random mutations in bacterial
DNA may confer resistance to an antibiotic. When exposed to the drug, bacteria
without resistance are killed, while those with resistance survive and multiply.
- Horizontal Gene Transfer: Bacteria can acquire resistance genes
from other bacteria through processes like conjugation,
transformation, or transduction. This spread of
resistance can lead to the rapid emergence of multidrug-resistant strains.
- Impact on Treatment:
- Ineffective Antibiotics: Antibiotic resistance limits the
effectiveness of current drugs, making infections harder to treat. Conditions
like tuberculosis, gonorrhea, and
pneumonia are becoming more difficult to cure due to resistance.
- Increased Mortality Rates: As resistance spreads, the number of
infections that are difficult to treat increases, leading to higher mortality
rates.
- Longer Hospital Stays and Higher Costs: Resistant infections
require longer treatments, often with more expensive and toxic drugs, leading to
higher healthcare costs and longer recovery periods.
22. Explain how vaccines work to protect individuals and communities
from infectious diseases. Discuss the different types of vaccines used in public
health.
Answer: Vaccines work by stimulating the immune system to
recognize and fight specific pathogens without causing the disease itself.
- Mechanism of Vaccination:
- Vaccines contain antigens from pathogens (e.g., inactivated
viruses, bacterial proteins, or weakened live microbes). These antigens
stimulate the immune system to produce antibodies and
memory cells.
- Upon future exposure to the actual pathogen, the immune system can mount a
faster and more effective response, preventing illness or reducing its severity.
- Types of Vaccines:
- Live Attenuated Vaccines: These contain weakened forms of the
pathogen that cannot cause disease but still trigger a strong immune response
(e.g., measles, mumps, rubella).
- Inactivated or Killed Vaccines: These vaccines contain
pathogens that have been killed or inactivated but still stimulate an immune
response (e.g., polio vaccine).
- Subunit, Recombinant, or Conjugate Vaccines: These contain
pieces of the pathogen, such as proteins or sugars, rather than the whole
organism (e.g., Hepatitis B, HPV vaccines).
- Toxoid Vaccines: These vaccines contain inactivated toxins
produced by the pathogen (e.g., tetanus, diphtheria).
23. Discuss the role of cytokines in the immune response. How do
cytokines contribute to the pathogenesis of diseases like sepsis and autoimmune
disorders?
Answer: Cytokines are small signaling molecules that regulate
immune responses and mediate communication between cells during inflammation and
immune activation.
- Role in the Immune Response:
- Cytokines include interleukins, interferons,
tumor necrosis factor (TNF), and chemokines,
which help coordinate immune responses by attracting immune cells to sites of
infection, promoting cell activation, and inducing fever.
- They can stimulate the activation of T-cells and
B-cells, enhance the function of macrophages and dendritic cells, and
facilitate tissue repair.
- Contribution to Disease Pathogenesis:
- In sepsis, an overproduction of cytokines (known as a
cytokine storm) can cause widespread inflammation, leading to tissue
damage, organ failure, and death.
- In autoimmune disorders, the immune system mistakenly produces
cytokines that activate immune cells against self-tissues. For example, in
rheumatoid arthritis, cytokines like TNF-α
promote inflammation in the joints, leading to pain and tissue destruction.
24. Describe the role of hemoglobin in the human body. What are the
implications of hemoglobinopathies such as sickle cell anemia and thalassemia on
human health?
Answer: Hemoglobin is a protein found in red blood cells (RBCs)
that binds to oxygen in the lungs and carries it to tissues throughout the body.
- Function of Hemoglobin:
- Hemoglobin consists of four polypeptide chains (two alpha and
two beta chains), each containing a heme group that can bind oxygen. Hemoglobin
picks up oxygen in the lungs and releases it in tissues with low oxygen
concentrations.
- Hemoglobin also helps in transporting carbon dioxide (a waste
product) from tissues back to the lungs for exhalation.
- Hemoglobinopathies:
- Sickle Cell Anemia: In this genetic disorder, a mutation in the
beta-globin gene leads to the production of sickle-shaped hemoglobin
(HbS). These sickle-shaped RBCs are less flexible, can block blood
flow, and are destroyed more rapidly, leading to anemia, pain,
and organ damage.
- Thalassemia: Thalassemia is caused by mutations in the genes
encoding either the alpha or beta globin chains, resulting in reduced or absent
hemoglobin production. This leads to microcytic anemia,
fatigue, and potential organ damage due to iron overload.
25. Explain how gene therapy is used to treat genetic disorders. Discuss
the challenges and potential risks associated with this technique.
Answer: Gene therapy is a technique that involves altering the
genes inside a person's cells to treat or prevent disease. It aims to correct or
replace defective genes that cause genetic disorders.
- Mechanisms of Gene Therapy:
- Gene Insertion: A healthy copy of a gene is inserted into the
patient's cells to compensate for a defective gene. This is typically achieved
using viral vectors that deliver the therapeutic gene into the
cells.
- Gene Editing: Techniques like CRISPR-Cas9
allow precise modification of genes by directly editing the DNA to correct
mutations or remove defective genes.
- Ex Vivo and In Vivo Approaches: In ex vivo gene therapy, cells
are modified outside the body and then reintroduced, whereas in vivo therapy
directly modifies genes within the patient’s body.
- Challenges and Risks:
- Immune Reactions: The body may recognize the viral vectors used
in gene therapy as foreign and mount an immune response against them,
potentially reducing the therapy’s effectiveness.
- Insertional Mutagenesis: There is a risk that inserted genes
may integrate into the wrong part of the genome, potentially leading to
cancer or other complications.
- Limited Effectiveness: In some cases, the introduced gene may
not express at the necessary levels, or the therapy may not reach the desired
cells, limiting its effectiveness.
- Ethical Concerns: Gene therapy raises ethical issues regarding
the possibility of germline editing (editing the DNA of
embryos) and the potential for genetic enhancement, rather than therapeutic
intervention.