An Overview of Recombinant DNA Technology Chapter Notes | Biology for Grade 9 PDF Download

An Overview of Recombinant DNA Technology

• Recombinant DNA (rDNA) technology, also known as genetic engineering, involves methods for directly manipulating the nucleic acid or genome of an organism.
• It emerged in the last century when scientists recognized DNA as the principal molecule responsible for expressing genetic traits.
• rDNA technology integrates concepts from molecular biology, microbiology, genetics, biochemistry, and other fields to manipulate genetic material.
• Key milestones in biological sciences that enabled rDNA technology include:
• Isolation and purification of nucleic acids, followed by understanding their structures, properties, and functions.
• DNA sequencing, which provided detailed insights into genetic codes.
• Establishing DNA as the carrier and propagator of genetic information across generations.
• Determination of the chemical and physical structure of DNA, notably the double helical structure proposed by Watson and Crick in 1953.
• Detailed understanding of DNA replication, transcription, and translation processes.
• Development of techniques to isolate and purify DNA from various organisms.
• Discovery of enzymes critical for DNA manipulation, including:
• Restriction enzymes, discovered by Werner Arber, Hamilton Smith, and Daniel Nathans in the late 1960s and early 1970s, which act as molecular scissors to cut DNA at specific sites.
• DNA ligase, discovered by Gellert, Lehman, Richardson, and Hurwitz in 1967, which joins DNA fragments.
• Scientists observed that bacteria can uptake foreign DNA from their environment and integrate it into their genome, prompting the question of whether genes could be transferred between organisms to express desired products.
• Stanley Cohen specialized in introducing plasmid DNA into Escherichia coli (E. coli) and propagating and cloning plasmids in bacteria.
• Herbert Boyer was skilled in using restriction enzymes to cleave double-stranded DNA, producing single-stranded ends with identical termini.
• Cohen and Boyer combined their expertise in 1973 to create the first recombinant plasmid by cutting a plasmid from one bacterial species, inserting a gene from another species, and closing the plasmid, resulting in the first genetically modified organism.
• rDNA technology has significantly impacted medicine and agriculture by enabling:
• Diagnosis and treatment of various diseases, including genetic disorders.
• Development of high-yielding, disease-free crops.
• Examples of rDNA contributions in medicine include:
• Production of human insulin in bacteria, overcoming the limitations of extracting insulin from animal pancreatic glands, which required large quantities and caused immunogenic reactions in humans.
• Production of human growth hormone in bacteria, eliminating the need for animal pituitary glands and reducing costs and contamination risks.
• Development of interferon for cancer treatment.
• Production of plasminogen activator and urokinase to dissolve blood clots.
• In agriculture, rDNA technology has facilitated targeted modifications in plant genomes, leading to:
• Genetically modified crops with resistance to diseases, reducing crop damage.
• Drought-resistant and salinity-tolerant crops, enabling cultivation in adverse environments.
• Improved quality and enhanced value of agricultural products.
• Future prospects include producing therapeutic proteins, peptides, and hormones in plants using rDNA technology, offering advantages over animal-based products in terms of cost and reduced risk of viral or protein contamination.
• Animal-based therapeutic products are generally costlier and require stringent measures to ensure freedom from viral and protein contaminants.

Key historical developments in biotechnology supporting rDNA technology include:

• 1917: Karl Ereky coined the term "Biotechnology."
• 1944: Avery, MacLeod, and McCarty demonstrated that DNA is the genetic material.
• 1952: Joshua Lederberg discovered plasmids.
• 1953: Watson and Crick proposed the double helical structure of DNA.
• 1960s: Werner Arber and Matthew Meselson discovered Type I restriction enzymes.
• 1967: Gellert, Lehman, Richardson, and Hurwitz discovered ligase enzymes.
• 1970: Hamilton O. Smith and Thomas J. Kelly discovered Type II restriction enzymes.
• 1972: Paul Berg assembled the first recombinant DNA from a bacterium into a virus.
• 1973: Stanley Cohen and Herbert Boyer developed DNA cloning and rDNA technology.
• 1975: Georges J.F. Köhler and César Milstein described hybridoma technology for monoclonal antibody production.
• 1982: FDA approved Humulin, the first recombinant DNA therapeutic product (insulin) by Eli Lilly and Genentech.
• 1983: Kary Mullis developed Polymerase Chain Reaction (PCR).
• 1984: Sir Alec Jeffreys invented DNA fingerprinting.
• 1986: The first recombinant vaccine, Recombivax HB, for Hepatitis B was approved.
• 1990: The Human Genome Project was initiated by the U.S. Department of Energy and National Institutes of Health.
• 1994: The Flavr Savr tomato, the first genetically engineered crop, was introduced by Calgene.
• 1996: Keith Campbell and Ian Wilmut cloned Dolly the sheep using somatic cell nuclear transfer.
• 1996: Monsanto developed Bt cotton, commercially released in China, the U.S., and later in India (2003).
• 2000: Ingo Potrykus and Peter Beyer developed Golden Rice.
• 2003: The Human Genome Project was completed.
• 2004: Avastin, an anti-VEGF monoclonal antibody for cancer treatment, was developed.
• 2006: Gardasil, a recombinant vaccine against human papillomavirus (HPV), received FDA approval.
• 2006: Nobel Prize awarded for the discovery of RNA interference (gene silencing) by double-stranded RNA.
• 2010: Robert Edwards received the Nobel Prize for developing human in vitro fertilization (IVF) therapy.
• 2012: Shinya Yamanaka and John B. Gurdon discovered that mature cells can be reprogrammed into induced pluripotent stem cells.
• 2019: Nobel Prize awarded for the discovery of the CRISPR-Cas9 genome editing tool.
• 2020: Recombinant vaccines against COVID-19 were developed.
• 2023: Nobel Prize awarded for the development of mRNA vaccines against COVID-19.