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Q5:
Discuss with your teacher what does ‘a suitable gene’ means, in the context of DNA vaccines.
Solution :
Theoretical Foundation: DNA Vaccine Mechanism
In the context of DNA vaccination, a ‘suitable gene’ refers to a specific deoxyribonucleic acid (DNA) sequence—typically a transgene—that encodes a viral, bacterial, or parasitic antigen capable of eliciting a robust, protective immune response in the host organism without causing the disease itself.
Step 1: Criteria for Identifying a ‘Suitable Gene’
For a gene to be considered suitable for vaccine development, it must fulfill the following biological and immunogenic requirements:
- Antigenicity: The gene must code for an epitope (or a collection of epitopes) that is recognized by the host's immune system as 'non-self' [Per the Principles of Immunological Self-Tolerance].
- Immunogenicity: The expressed protein must be capable of inducing both humoral (B-cell mediated) and cell-mediated (T-cell mediated) immune responses.
- Conservation: The gene sequence should target highly conserved regions of the pathogen to ensure the vaccine remains effective against various strains or mutations of the pathogen.
- Safety: The gene must not encode virulence factors or oncogenic sequences that could lead to pathogenicity or unintended side effects in the host.
Step 2: Molecular Configuration of the DNA Vector
A suitable gene is insufficient on its own; it must be cloned into a plasmid vector equipped with regulatory elements. The following structure is required:
| Component | Function |
|---|---|
| Promoter | Ensures high-level expression of the target gene in eukaryotic cells (e.g., CMV or SV40 promoters) [Per the Central Dogma of Molecular Biology]. |
| Target Gene | The specific coding sequence (CDS) for the selected antigenic protein. |
| Poly-A Signal | Facilitates the termination of transcription and stabilization of the mRNA transcript. |
| Antibiotic Resistance Gene | Used as a selectable marker during the cloning process in bacterial cultures. |
Step 3: Visual Representation of DNA Vaccine Vector Integration
Step 4: The Process of Expression and Immunization
- Delivery: The plasmid containing the ‘suitable gene’ is injected into the host [Typically intramuscularly or intradermally].
- Cellular Uptake: Host cells (myocytes or antigen-presenting cells) take up the DNA via endocytosis.
- Transcription and Translation: The host cell’s transcriptional machinery [RNA Polymerase II] processes the gene to produce mRNA, which is then translated into the antigenic protein.
- Presentation: The expressed protein is processed and presented on the cell surface via MHC Class I and II molecules, triggering a memory T-cell and B-cell response [Per the Adaptive Immune Response Mechanism].
Final Solution: In the context of DNA vaccines, a ‘suitable gene’ is a non-pathogenic, highly immunogenic DNA sequence derived from a pathogen, flanked by eukaryotic regulatory elements (promoter/poly-A signal), which, when expressed by the host's cells, generates an antigen that primes the immune system for future exposure to the actual pathogen.
More Questions from Class 12 Biology Human Health and Disease EXERCISES
- Q1: What are the various public health measures, which you would suggest as safeguard against infectious diseases?
- Q1: What are the various public health measures, which you would suggest as safeguard against infectious diseases?
- Q2: In which way has the study of biology helped us to control infectious diseases?
- Q2: In which way has the study of biology helped us to control infectious diseases?
- Q3(a): How does the transmission of each of the following diseases take place? (a) Amoebiasis
- Q3(a): How does the transmission of each of the following diseases take place? (a) Amoebiasis
- Q3(b): How does the transmission of each of the following diseases take place? (b) Malaria
- Q3(b): How does the transmission of each of the following diseases take place? (b) Malaria
- Q3(c): How does the transmission of each of the following diseases take place? (c) Ascariasis
- Q3(c): How does the transmission of each of the following diseases take place? (c) Ascariasis
- Q3(d): How does the transmission of each of the following diseases take place? (d) Pneumonia
- Q3(d): How does the transmission of each of the following diseases take place? (d) Pneumonia
- Q4: What measure would you take to prevent water-borne diseases?
- Q4: What measure would you take to prevent water-borne diseases?
- Q5: Discuss with your teacher what does ‘a suitable gene’ means, in the context of DNA vaccines.
- Q6: Name the primary and secondary lymphoid organs.
- Q6: Name the primary and secondary lymphoid organs.
- Q7(a): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (a) MALT
- Q7(a): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (a) MALT
- Q7(b): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (b) CMI
- Q7(b): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (b) CMI
- Q7(c): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (c) AIDS
- Q7(c): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (c) AIDS
- Q7(d): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (d) NACO
- Q7(d): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (d) NACO
- Q7(e): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (e) HIV
- Q7(e): The following are some well-known abbreviations, which have been used in this chapter. Expand each one to its full form: (e) HIV
- Q8(a): Differentiate the following and give examples of each: (a) Innate and acquired immunity
- Q8(a): Differentiate the following and give examples of each: (a) Innate and acquired immunity
- Q8(b): Differentiate the following and give examples of each: (b) Active and passive immunity
- Q8(b): Differentiate the following and give examples of each: (b) Active and passive immunity
- Q9: Draw a well-labelled diagram of an antibody molecule.
- Q9: Draw a well-labelled diagram of an antibody molecule.
- Q10: What are the various routes by which transmission of human immuno-deficiency virus takes place?
- Q10: What are the various routes by which transmission of human immuno-deficiency virus takes place?
- Q11: What is the mechanism by which the AIDS virus causes deficiency of immune system of the infected person?
- Q11: What is the mechanism by which the AIDS virus causes deficiency of immune system of the infected person?
- Q12: How is a cancerous cell different from a normal cell?
- Q12: How is a cancerous cell different from a normal cell?
- Q13: Explain what is meant by metastasis.
- Q13: Explain what is meant by metastasis.
- Q14: List the harmful effects caused by alcohol/drug abuse.
- Q14: List the harmful effects caused by alcohol/drug abuse.
- Q15: Do you think that friends can influence one to take alcohol/drugs? If yes, how may one protect himself/herself from such an influence?
- Q15: Do you think that friends can influence one to take alcohol/drugs? If yes, how may one protect himself/herself from such an influence?
- Q16: Why is that once a person starts taking alcohol or drugs, it is difficult to get rid of this habit? Discuss it with your teacher.
- Q16: Why is that once a person starts taking alcohol or drugs, it is difficult to get rid of this habit? Discuss it with your teacher.
- Q17: In your view what motivates youngsters to take to alcohol or drugs and how can this be avoided?
- Q17: In your view what motivates youngsters to take to alcohol or drugs and how can this be avoided?
CBSE Solutions for Class 12 Biology Human Health and Disease
Chapters in CBSE - Class 12 Biology
- Reproduction in Organisms
- Human Reproduction
- Reproductive Health
- Principles of Inheritance and Variation
- Molecular Basis of Inheritance
- Evolution
- Strategies for Enhancement in Food Production
- Microbes in Human Welfare
- Biotechnology: Principles and Processes
- Biotechnology and Its Applications
- Organisms and Populations
- Ecosystem
- Biodiversity and Conservation
- Environmental Issues
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