Chapter 1
An Overview of Recombinant DNA Technology
EXERCISES
1. Discuss in brief how recombinant DNA technology was initially developed?
Answer: The early development of recombinant DNA technology was a fascinating story of scientific collaboration and groundbreaking discoveries. Here’s a closer look at the key players and milestones:
The Players:
*Paul Berg: A biochemist at Stanford University, Berg conducted foundational research on DNA ligase and was involved in creating the first recombinant molecules.
*Stanley Cohen: A biochemist at the University of California, San Francisco, Cohen developed techniques for isolating plasmids and pioneered their use as vectors for foreign DNA.
*Herbert Boyer: A microbiologist at UCSF, Boyer collaborated with Cohen to develop methods for inserting genes into plasmids and transferring them into bacteria.
The Milestones:
*1950s: The double helix structure of DNA is revealed, providing a crucial understanding of genetic information.
*Late 1950s: Restriction enzymes, which precisely cut DNA at specific sites, are discovered.
*1967: DNA ligase, the enzyme that joins DNA fragments, is identified.
*1960s: Plasmids, small, circular DNA molecules that can replicate independently, are discovered.
*1972: Berg and Cohen successfully combine DNA from a frog and a bacterium, creating the first recombinant DNA molecule.
*1973: Cohen and Boyer develop methods for inserting genes into plasmids and transferring them into bacteria, allowing for the expression of foreign genes in these cells.
*1975: The Asilomar Conference establishes safety guidelines and ethical considerations for recombinant DNA research.
*Late 1970s: The first recombinant products, like human insulin produced by genetically modified bacteria, are introduced.
Key Takeaway:
Recombinant DNA technology didn’t arise overnight. It was a gradual process built on the efforts of numerous scientists and the convergence of discoveries like DNA structure, restriction enzymes, plasmid vectors, and DNA splicing techniques. This collaborative effort paved the way for a revolutionary technology that continues to impact medicine, agriculture, and biotechnologies to this day.
2. Briefly discuss the application of DNA technology in crop improvement and therapeutic.
Answer: Applications of DNA Technology: Crop Improvement and Therapeutics
DNA technology has revolutionized both crop improvement and therapeutics. Here’s a brief overview of its applications in each field:
Crop Improvement:
*Increased yield and quality: Genetic modification (GM) crops can resist pests and diseases, tolerate environmental stresses like drought and salinity, and enhance nutritional content (e.g., Golden Rice with beta-carotene). This can lead to higher yields and improved food quality.
*Reduced pesticide use: GM crops engineered for pest resistance can significantly reduce the reliance on chemical pesticides, benefiting both human health and the environment.
*Faster breeding: DNA markers can identify desirable traits in crops, accelerating the breeding process and allowing for development of new varieties with specific characteristics.
*Improved resource utilization: Crops can be engineered for more efficient water and nutrient use, leading to sustainable agriculture practices.
Therapeutics:
*Gene therapy: Gene therapy involves the introduction of functional copies of genes to replace defective ones causing genetic diseases. This has shown promise for treating conditions like cystic fibrosis, hemophilia, and some cancers.
*Diagnosis and screening: DNA-based diagnostic tests can detect genetic mutations and predispositions to diseases, allowing for early diagnosis and preventative measures.
*Drug development: Understanding the genetic basis of diseases can facilitate the development of targeted drugs and personalized medicine approaches.
*Production of therapeutic proteins: Recombinant DNA technology allows for the production of valuable therapeutic proteins like insulin, hormones, and antibodies, improving treatments for various conditions.
Challenges and Considerations:
Despite the immense potential, both crop improvement and therapeutic applications of DNA technology face challenges:
*Ethical concerns: GM crops raise concerns about safety, environmental impact, and corporate control of food systems. Gene therapy also raises ethical considerations regarding potential unintended consequences and germline editing.
*Regulations: Stringent regulations govern the development and use of GM crops and gene therapy treatments, often leading to lengthy and expensive approval processes.
*Accessibility: Access to advanced DNA technologies and their benefits can be limited in developing countries due to financial and infrastructure constraints.
Overall, DNA technology offers tremendous possibilities for improving agriculture and treating diseases. However, addressing ethical concerns, ensuring responsible development and regulation, and promoting equitable access are crucial for maximizing the benefits of this powerful technology.
3. Who discovered the Plasmid?
(a) Paul Berg
(b) Sir Alec Jeffreys
(c) Joshua Lederberg
(d) Kary Mullis
Answer: (c) Joshua Lederberg.
4. Plasminogen activator and Urokinase are used as:
(a) Antiviral agent
(b) Blood clot dissolving drug
(c) Sugar lowering agent
(d) Cholesterol lowering agent
Answer: (b) Blood clot dissolving drug
5. Assertion: Restriction endonuclease cuts DNA and isolated mostly from bacteria.
Reason: Restriction endonuclease is a type of nuclease.
(a) Both assertion and reason are true and the reason is the correct explanation of the assertion.
(b) Both assertion and reason are true but the reason is not the correct explanation of the assertion.
(c) Assertion is true but reason is false.
(d) Both assertion and reason are false.
Answer: (c) Assertion is true but reason is false.
6. Assertion: E.coli divides in 20 minutes while replicates its DNA in about 60 minutes.
Reason: E.coli follows multifork replication mechanism.
(a) Both assertion and reason are true and the reason is the correct explanation of the assertion.
(b) Both assertion and reason are true but the reason is not the correct explanation of the assertion.
(c) Assertion is true but reason is false.
(d) Both assertion and reason are false.
Answer: (b) Both assertion and reason are true but the reason is not the correct explanation of the assertion.