Gene Therapy – Detailed Notes
Definition
Gene therapy is a therapeutic technique in which genetic material (DNA or RNA) is introduced, removed, or modified in a patient’s cells to treat or prevent genetic disorders and diseases by correcting defective genes or providing new functional genes.
Basic Concept
Many diseases occur due to mutation, deletion, or malfunction of genes.
Gene therapy aims to:
Replace a defective gene
Add a functional gene
Silence or inhibit a harmful gene
It works at the molecular level, targeting the root cause of disease rather than symptoms.
Types of Gene Therapy
1. Somatic Gene Therapy
Gene transfer into somatic (body) cells.
Effects are not inherited.
Most widely used and ethically accepted.
Examples:
Cystic fibrosis, cancer therapy, SCID
2. Germline Gene Therapy
Gene transfer into germ cells (sperm/egg) or early embryos.
Genetic changes are heritable.
Ethically restricted and banned in many countries.
Approaches of Gene Therapy
1. Gene Replacement Therapy
Defective gene is replaced by a normal functional gene.
2. Gene Addition Therapy
A new gene is added without removing the defective one.
3. Gene Silencing Therapy
Harmful gene expression is suppressed using:
siRNA
antisense oligonucleotides
CRISPR interference
4. Gene Editing
Precise correction of genes using:
CRISPR-Cas9
TALENs
Zinc-finger nucleases
Delivery Methods of Gene Therapy
A. Viral Vectors
Viruses modified to be non-pathogenic and used as gene carriers.
Vector
Features
Applications
Retrovirus
Integrates into genome
Cancer, SCID
Lentivirus
Infects dividing & non-dividing cells
HIV, genetic disorders
Adenovirus
High expression, non-integrating
Cancer therapy
AAV
Low immunogenicity
Eye and muscle diseases
B. Non-Viral Methods
Liposomes (lipofection)
Electroporation
Naked DNA injection
Gene gun (biolistics)
Strategies of Gene Delivery
1. Ex Vivo Gene Therapy
Cells removed from patient
Genetically modified in laboratory
Reintroduced into patient
Example: SCID treatment
2. In Vivo Gene Therapy
Gene directly delivered into patient’s body
Example: Eye gene therapy (retinal disorders)
Steps Involved in Gene Therapy
Identification of defective gene
Cloning of therapeutic gene
Selection of suitable vector
Gene delivery to target cells
Expression of therapeutic gene
Monitoring for safety and efficacy
Applications of Gene Therapy
1. Genetic Disorders
Severe Combined Immunodeficiency (SCID)
Hemophilia
Cystic fibrosis
Muscular dystrophy
2. Cancer
Tumor suppressor gene delivery (p53)
Suicide gene therapy
Immunogene therapy
3. Infectious Diseases
HIV gene therapy
Hepatitis
4. Neurological Disorders
Parkinson’s disease
Alzheimer’s disease
Advantages
Treats disease at genetic level
Long-lasting or permanent cure
Highly specific
Reduces dependency on drugs
Potential to cure inherited disorders
Limitations
Immune response against vectors
Risk of insertional mutagenesis
High cost
Ethical concerns
Limited efficiency in some tissues
Ethical, Legal, and Social Issues
Germline gene therapy ethics
Gene editing in embryos
Accessibility and affordability
Long-term safety concerns
Genetic enhancement misuse
Recent Advances
CRISPR-Cas9 gene editing
CAR-T cell therapy
RNA-based therapies
Personalized gene therapy
Examples of Approved Gene Therapies
Luxturna – inherited retinal disease
Zolgensma – spinal muscular atrophy
CAR-T therapy – leukemia and lymphoma
Conclusion
Gene therapy represents a revolutionary approach in modern medicine, offering potential cures for genetic and chronic diseases. Although challenges such as safety, cost, and ethical issues remain, advances in gene editing and vector technology continue to improve its effectiveness and clinical success.
Gene therapy is used to:
A) Remove proteins
B) Modify genetic material
C) Destroy cells
D) Inhibit enzymes
Answer: B
Gene therapy treats disease by:
A) Drug action
B) Surgical removal
C) Correcting defective genes
D) Vaccination
Answer: C
Gene therapy acts at the:
A) Cellular level
B) Tissue level
C) Molecular level
D) Organ level
Answer: C
Genetic material used in gene therapy includes:
A) DNA only
B) RNA only
C) DNA or RNA
D) Proteins only
Answer: C
Replacement of a faulty gene is called:
A) Gene silencing
B) Gene replacement
C) Gene suppression
D) Gene knockout
Answer: B
Types of Gene Therapy
Gene therapy performed on body cells is called:
A) Germline gene therapy
B) Somatic gene therapy
C) Embryonic gene therapy
D) Reproductive gene therapy
Answer: B
Changes in somatic gene therapy are:
A) Heritable
B) Non-heritable
C) Permanent in offspring
D) Transmitted to next generation
Answer: B
Germline gene therapy affects:
A) Only patient
B) Only parents
C) Future generations
D) Cancer cells
Answer: C
Germline gene therapy is:
A) Widely accepted
B) Ethically restricted
C) Commonly practiced
D) Approved worldwide
Answer: B
Most current clinical gene therapy trials use:
A) Germline therapy
B) Somatic therapy
C) Embryonic therapy
D) Reproductive therapy
Answer: B
Approaches & Strategies
Addition of a normal gene without removing faulty one is:
A) Gene replacement
B) Gene addition
C) Gene deletion
D) Gene knockout
Answer: B
Suppression of harmful gene expression is called:
A) Gene addition
B) Gene silencing
C) Gene replacement
D) Gene activation
Answer: B
Tools used for gene editing include:
A) CRISPR-Cas9
B) TALENs
C) Zinc-finger nucleases
D) All of the above
Answer: D
Ex vivo gene therapy involves:
A) Direct injection into patient
B) Modification outside the body
C) Germline manipulation
D) Embryo editing
Answer: B
In vivo gene therapy involves:
A) Cell culture only
B) Direct delivery into patient
C) Gamete modification
D) Cloning
Answer: B
Vectors & Delivery Systems
Most commonly used vectors are:
A) Bacterial plasmids
B) Viral vectors
C) Ribosomes
D) Enzymes
Answer: B
Retroviral vectors integrate into:
A) Cytoplasm
B) Host genome
C) Mitochondria
D) Ribosomes
Answer: B
Lentiviruses can infect:
A) Dividing cells only
B) Non-dividing cells only
C) Both dividing and non-dividing cells
D) Bacterial cells
Answer: C
Adenoviral vectors generally:
A) Integrate into genome
B) Do not integrate into genome
C) Cause mutations always
D) Are non-immunogenic
Answer: B
AAV vectors are preferred because of:
A) High toxicity
B) Low immunogenicity
C) Large genome size
D) Rapid degradation
Answer: B
Non-Viral Methods
Liposome-mediated gene delivery is called:
A) Electroporation
B) Lipofection
C) Biolistics
D) Microinjection
Answer: B
Electroporation introduces DNA using:
A) Chemical treatment
B) Electric pulses
C) Heat shock
D) Ultrasound
Answer: B
Gene gun method is also called:
A) Lipofection
B) Microinjection
C) Biolistics
D) Transduction
Answer: C
Naked DNA delivery is mainly used in:
A) Muscles
B) Brain
C) Liver only
D) Kidney
Answer: A
Non-viral methods generally have:
A) Higher immunogenicity
B) Lower safety
C) Lower efficiency than viral vectors
D) Higher mutation rates
Answer: C
Applications
First successful gene therapy treated:
A) Hemophilia
B) SCID
C) Cystic fibrosis
D) Cancer
Answer: B
Gene therapy for cancer may involve:
A) Tumor suppressor genes
B) Suicide genes
C) Immune activation
D) All of the above
Answer: D
CAR-T cell therapy is used for:
A) Genetic disorders
B) Cancer treatment
C) Viral infection
D) Diabetes
Answer: B
Gene therapy in retinal disorders uses:
A) Retrovirus
B) Adenovirus
C) AAV
D) Lentivirus
Answer: C
Hemophilia gene therapy targets:
A) Clotting factor genes
B) Insulin genes
C) Antibody genes
D) Enzyme genes
Answer: A
Advantages
Main advantage of gene therapy is:
A) Temporary relief
B) Symptomatic treatment
C) Treats root cause of disease
D) Low cost
Answer: C
Gene therapy can provide:
A) Permanent cure
B) Short-term cure only
C) No cure
D) Temporary suppression only
Answer: A
Gene therapy reduces dependence on:
A) Surgery
B) Antibiotics
C) Long-term drug therapy
D) Vaccines
Answer: C
Target specificity of gene therapy is:
A) Low
B) Moderate
C) High
D) Random
Answer: C
Personalized medicine is possible due to:
A) Vaccines
B) Gene therapy
C) Antibiotics
D) Hormone therapy
Answer: B
Limitations & Ethics
Major risk of gene therapy is:
A) Infection
B) Insertional mutagenesis
C) Vitamin deficiency
D) Allergy only
Answer: B
Immune response occurs mainly against:
A) DNA
B) RNA
C) Viral vectors
D) Proteins
Answer: C
High cost is a:
A) Benefit
B) Ethical issue
C) Technical advantage
D) Safety feature
Answer: B
Germline gene therapy is controversial because it:
A) Is expensive
B) Affects future generations
C) Is inefficient
D) Requires viruses
Answer: B
Gene therapy trials require strict:
A) Laboratory rules
B) Ethical guidelines
C) Political approval
D) Trade regulations
Answer: B
Recent Advances & General
CRISPR-Cas9 is used for:
A) Gene cloning
B) Gene editing
C) Protein synthesis
D) DNA sequencing
Answer: B
RNA-based gene therapy includes:
A) siRNA therapy
B) mRNA therapy
C) Antisense therapy
D) All of the above
Answer: D
Zolgensma is approved for treating:
A) Cancer
B) Spinal muscular atrophy
C) Hemophilia
D) SCID
Answer: B
Luxturna is used to treat:
A) Muscular dystrophy
B) Retinal disease
C) Diabetes
D) Cancer
Answer: B
CAR-T therapy modifies:
A) B cells
B) T cells
C) Stem cells
D) Neurons
Answer: B
Final
Gene therapy is an example of:
A) Preventive medicine
B) Molecular medicine
C) Herbal medicine
D) Surgical therapy
Answer: B
Long-term expression in gene therapy requires:
A) Protein injection
B) Gene integration
C) Drug administration
D) Vaccination
Answer: B
Safety of gene therapy depends mainly on:
A) Vector choice
B) Age of patient
C) Diet
D) Temperature
Answer: A
Gene therapy is still limited by:
A) Technology
B) Ethical issues
C) Cost
D) All of the above
Answer: D
Future of gene therapy is closely linked with:
A) Antibiotics
B) Vaccines
C) Gene editing technologies
D) Herbal medicine
Answer: C
Comments