3. Biology Notes 07

Elaborate Notes

Biotechnology and Genetic Engineering

Biotechnology, in its broadest sense, is the utilization of biological systems, living organisms, or their derivatives to create or modify products and processes for specific uses. The term was coined by Hungarian agricultural engineer Károly Ereky in 1919. While traditional biotechnology includes practices like selective breeding and fermentation, modern biotechnology is largely driven by Genetic Engineering. This is the direct manipulation of an organism’s genes using biotechnology. It involves altering the genetic makeup (DNA/RNA) of an organism. The application of this scientific knowledge for practical purposes, such as in medicine, agriculture, and industry, is termed Applied Biotechnology. One of the core techniques in this field is molecular cloning, which involves creating multiple copies of a specific DNA fragment.

Recombinant DNA Technology

Recombinant DNA (rDNA) technology is a cornerstone of modern genetic engineering. It involves the process of joining together DNA molecules from two different species, which are then inserted into a host organism to produce new genetic combinations. This technology, pioneered by Stanley Cohen and Herbert Boyer in 1973, allows for the alteration of genetic material outside of an organism to introduce enhanced or desired characteristics. The fundamental principle is the insertion of a specific DNA fragment (the “gene of interest”) from a source organism into a carrier DNA molecule called a vector. This combined molecule, known as recombinant DNA, is then introduced into a host cell (like a bacterium), which will replicate it, thereby producing the desired protein or trait.

The steps involved are as follows:

• Isolation of the Gene of Interest: The first step is to identify and isolate the specific gene that codes for a desired trait. For instance, the gene responsible for producing Human Growth Hormone can be isolated from human cells.
• Cutting the DNA: A specific class of enzymes called restriction enzymes, or nucleases, act as “molecular scissors” to cut the DNA at specific recognition sites, excising the gene of interest.
• Vector Insertion: The isolated gene is then inserted into a vector. A vector is a DNA molecule used as a vehicle to artificially carry foreign genetic material into another cell. Plasmids, which are small, circular, extrachromosomal DNA molecules found in bacteria, are commonly used as vectors. The same restriction enzyme is used to cut the plasmid, creating complementary “sticky ends.”
• Ligation: The gene of interest and the cut plasmid are joined together by an enzyme called DNA ligase. This enzyme forms phosphodiester bonds, effectively “pasting” the gene into the vector, creating a recombinant DNA molecule.
• Transformation: This recombinant vector is then introduced into a host organism, typically a bacterium like E. coli, which will then multiply and express the inserted gene.

Viral Vector Vaccines

This technology utilizes a modified, harmless virus (the vector) to deliver genetic instructions to our cells.

• Mechanism: Instead of injecting the actual pathogen, a gene coding for a specific antigen (a protein from the pathogen that triggers an immune response) is identified. This gene is inserted into a harmless viral vector. When this recombinant virus is introduced into the body, it instructs human cells to produce the antigen. The immune system’s B cells recognize this antigen as foreign and produce antibodies and memory cells against it. This process creates immunity without causing the actual disease.
• Vector Choice: Adenoviruses, particularly those from other species like chimpanzees (as used in the Oxford-AstraZeneca vaccine, Covishield), are often chosen as vectors. This is because humans are less likely to have pre-existing immunity to a non-human adenovirus, ensuring the vector is not destroyed before it can deliver the genetic payload. The immune system thus focuses its attack on the target antigen produced by our cells, not the vector itself.
• Comparison: This differs from live attenuated vaccines, which use a weakened version of the entire living virus (e.g., Measles, Mumps, Rubella vaccine).
• Examples: Covishield (using a chimpanzee adenovirus vector) and Sputnik V (using two different human adenovirus vectors for its two doses) are prominent examples of viral vector vaccines developed for COVID-19. Side effects like fever and headaches are manifestations of the body’s immune system actively building a response.

Gene Editing and CRISPR-Cas9

Gene editing is a group of technologies that gives scientists the ability to change an organism’s DNA by adding, removing, or altering genetic material at particular locations in the genome.

• CRISPR: The most prominent tool is CRISPR-Cas9 (Clustered Regularly Interspaced Short Palindromic Repeats and CRISPR-associated protein 9). This system was originally discovered as a natural defense mechanism in bacteria and archaea against invading viruses. For their groundbreaking work in developing this method for genome editing, Emmanuelle Charpentier and Jennifer A. Doudna were awarded the Nobel Prize in Chemistry in 2020.
• The Process: The CRISPR-Cas9 system has two key components:
  1. Cas9 Protein: An enzyme that acts as “molecular scissors” to cut the two strands of DNA at a specific location in the genome.
  2. Guide RNA (gRNA): A small piece of pre-designed RNA sequence that binds to a specific target DNA sequence. The gRNA “guides” the Cas9 enzyme to the right part of the genome, ensuring the cut is made at the precise location of the defective or targeted gene.
• After the cut is made by Cas9, the cell’s natural DNA repair mechanism is used to add or delete pieces of genetic material, or to replace an existing segment with a customized DNA sequence, joined by the ligase enzyme. While this technology holds immense promise for curing genetic diseases, it is largely in the experimental stage for human therapeutic applications.

Designer Babies and Gene Therapy

• Designer Babies: This term refers to the hypothetical use of gene editing on an embryo in vitro to select for specific traits, ranging from eliminating disease risk to enhancing physical or cognitive attributes. This practice raises profound ethical questions about eugenics, consent of the unborn child, and social equity. Due to these concerns, a global consensus-based moratorium on heritable human genome editing is currently in place.
• Gene Therapy: This is a therapeutic technique that uses genes to treat or prevent disease. In its most common form, it involves introducing a new, functional gene into a patient’s cells to correct the effects of a disease-causing mutation. For example, in the treatment of Cystic Fibrosis, a functional copy of the CFTR gene is delivered to the affected lung cells to compensate for the non-functional gene. Importantly, this therapy typically does not alter the original defective gene and is not heritable (somatic gene therapy).

Cloning

Cloning is the process of producing genetically identical individuals of an organism either naturally or artificially. In contrast to sexual reproduction where two parents contribute genetic material (via haploid gametes), cloning involves a single parent providing the complete set of genetic material (from a diploid somatic cell).

• Animal Cloning Process (Somatic Cell Nuclear Transfer - SCNT):
  1. A somatic cell (any body cell other than a gamete) is taken from the animal to be cloned. Its nucleus contains the complete diploid set of chromosomes.
  2. An unfertilized egg cell is taken from a female donor.
  3. The nucleus of this egg cell is removed through a process called enucleation.
  4. The nucleus from the somatic cell is then transferred into the enucleated egg.
  5. This reconstructed egg is stimulated with an electric shock or chemicals to trigger cell division, developing into an embryo.
  6. The embryo is implanted into the uterus of a surrogate mother, where it develops to term.
• The resulting offspring is a genetically identical clone of the animal from which the somatic cell was taken. The first mammal to be successfully cloned using SCNT was Dolly the sheep, born in 1996 at the Roslin Institute in Scotland.
• Challenges: Cloning has a very low success rate; hundreds of embryos were created before Dolly was successfully born. Cloned animals have often exhibited premature aging and lower immunity. Human cloning remains theoretical and is banned in most countries due to ethical and safety concerns.

Three-Parent Baby (Mitochondrial Replacement Therapy)

This technology aims to prevent the transmission of mitochondrial diseases from mother to child.

• Mitochondrial DNA (mtDNA): Mitochondria, the cell’s powerhouses, contain their own small set of DNA (37 genes in humans). mtDNA is inherited exclusively from the mother via the egg’s cytoplasm. Defects in mtDNA can cause severe, debilitating conditions like Leigh syndrome.
• The Technology: Mitochondrial Replacement Therapy (MRT) involves creating an embryo with nuclear DNA from the intended parents and healthy mitochondrial DNA from a female donor. There are two main methods:
  1. Maternal Spindle Transfer: The nucleus (containing the mother’s nuclear DNA) is removed from the mother’s unfertilized egg and transferred into a donor’s enucleated egg (which has healthy mitochondria). This reconstructed egg is then fertilized with the father’s sperm.
  2. Pronuclear Transfer: The mother’s egg is first fertilized with the father’s sperm. The resulting pronuclei (containing the genetic material of both parents) are then removed from the zygote and transferred into a donor zygote that has also been fertilized but has had its own pronuclei removed.
• The resulting baby has genetic material from three individuals: nuclear DNA from the mother and father, and mtDNA from the donor. The United Kingdom was the first country to legally approve this procedure in 2015.

Stem Cells

Stem cells are undifferentiated or partially differentiated cells that can differentiate into various cell types and proliferate indefinitely to produce more of the same stem cell.

• Types of Stem Cells:
  • Embryonic Stem Cells (ESCs): Derived from the inner cell mass of a blastocyst (an early-stage embryo). They are pluripotent, meaning they can differentiate into all derivatives of the three primary germ layers (ectoderm, endoderm, and mesoderm).
  • Adult Stem Cells: Found in various tissues (e.g., bone marrow, skin) in a fully developed organism. They are generally multipotent, meaning they can differentiate into a limited range of cell types specific to their tissue of origin.
  • Induced Pluripotent Stem Cells (iPSCs): These are adult cells (e.g., skin or blood cells) that have been reprogrammed back into an embryonic-like pluripotent state. This breakthrough, developed by Shinya Yamanaka’s team in 2006, allows for the creation of patient-specific stem cells without using embryos.
• Applications: Stem cell technology holds potential for regenerative medicine, allowing for the repair or replacement of damaged tissues and organs. A common source of easily accessible stem cells is the umbilical cord blood, collected after birth. The practice of cryogenically preserving this blood for future use is known as placenta banking or cord blood banking.

Genetically Modified (GM) Organisms and Crops

A Genetically Modified Organism (GMO) is any organism whose genetic material has been altered using genetic engineering techniques.

• GM Crops: In agriculture, this involves inserting a gene from another species into a plant’s genome to confer a desired trait.
• Objectives:
  • Pest Resistance: Bt Cotton contains a gene from the soil bacterium Bacillus thuringiensis, which produces a protein toxic to certain insects like bollworms.
  • Nutritional Enhancement (Biofortification): Golden Rice is genetically engineered to produce beta-carotene, a precursor of Vitamin A, to combat vitamin A deficiency.
  • Herbicide Tolerance: Crops can be made resistant to specific herbicides, allowing farmers to control weeds without harming the crop.
  • Improved Shelf Life: The Flavr Savr tomato, commercialized in 1994, was engineered to ripen more slowly.
• Status in India: The only GM crop approved for commercial cultivation in India is Bt Cotton. Other crops like Bt Brinjal and GM Mustard (DMH-11) have faced regulatory hurdles and public opposition.
• Concerns: Issues include potential harm to non-target organisms, the risk of gene flow to wild relatives, long-term health effects, and economic dependency on multinational corporations that own the patents. A major controversy surrounded “terminator technology”, a method to create sterile seeds, forcing farmers to buy new seeds each year.

Prelims Pointers

• Recombinant DNA Technology: Requires restriction enzymes (nucleases) for cutting and DNA ligase for joining DNA segments.
• Vectors: Plasmids are common vectors used to carry foreign DNA into host cells.
• Viral Vector Vaccines: Use a modified, harmless virus (e.g., adenovirus) to deliver a gene coding for a specific antigen.
• Vaccine Examples: Covishield and Sputnik V are viral vector vaccines.
• Gene Editing Tool: CRISPR-Cas9 is a prominent gene-editing technology.
• CRISPR Components: It uses a Cas9 enzyme (protein) to cut DNA and a guide RNA (gRNA) to target the specific location.
• Nobel Prize (2020, Chemistry): Awarded to Emmanuelle Charpentier and Jennifer Doudna for developing the CRISPR-Cas9 method.
• Cloning: The process of creating a genetically identical copy of an organism.
• SCNT: Somatic Cell Nuclear Transfer is the primary method for animal cloning.
• First Cloned Mammal: Dolly the sheep, born in 1996 in Scotland.
• Three-Parent Baby: A baby with nuclear DNA from two parents and mitochondrial DNA (mtDNA) from a third donor.
• Mitochondrial DNA (mtDNA): Inherited exclusively from the mother.
• MRT: Mitochondrial Replacement Therapy is the technology used for creating a three-parent baby. It includes Maternal Spindle Transfer and Pronuclear Transfer.
• Stem Cells: Undifferentiated cells with the potential to develop into many different cell types.
• Pluripotent Stem Cells: Can form any cell type in the body (e.g., Embryonic Stem Cells).
• iPSCs: Induced Pluripotent Stem Cells are adult cells reprogrammed to a pluripotent state.
• Placenta Banking: Cryopreservation of stem cells from umbilical cord blood.
• GM Crop in India: Only Bt Cotton is approved for commercial cultivation.
• Bt Toxin: The protein produced by the gene from Bacillus thuringiensis bacterium, which is toxic to certain pests.
• Golden Rice: Genetically modified to be fortified with Vitamin A precursor (beta-carotene).
• Terminator Seeds: A controversial technology for producing plants with sterile seeds.
• Biotechnology Color Codes: Blue (Marine), Green (Agriculture), Red (Medical), White (Industrial), Grey (Environmental).

Mains Insights

GS Paper III: Science & Technology

• Application-based Analysis: Biotechnology offers transformative solutions in agriculture (GM crops for food security and climate resilience), health (gene therapy for genetic disorders, affordable vaccines, personalized medicine), and environment (bioremediation). However, it is crucial to analyze the cost-benefit ratio and societal preparedness for these technologies.
• GM Crops Debate:
  • Arguments For: Increased yield, reduced pesticide use (e.g., Bt Cotton), enhanced nutrition (Golden Rice), and resilience to climate change can address India’s food security challenges.
  • Arguments Against: Potential ecological disruption (impact on biodiversity), health concerns (allergenicity), and socio-economic issues like farmer dependency on MNCs for seeds and the threat to traditional crop varieties.
  • Regulatory Framework: India’s regulatory body, the Genetic Engineering Appraisal Committee (GEAC), faces challenges in balancing scientific approval with public perception and political considerations. A transparent, science-based, and robust regulatory pathway is essential for harnessing the benefits while mitigating risks.
• Intellectual Property Rights (IPR) Issues:
  • Biopiracy: The patenting of traditional knowledge or biological resources (e.g., Neem, Turmeric) by foreign corporations without proper authorization or benefit-sharing with indigenous communities is a significant concern. The Biological Diversity Act, 2002, aims to address this.
  • Patenting Life Forms: The ethical and legal debate over patenting genetically modified organisms and DNA sequences raises questions about ownership of life and can stifle innovation and access for public good.

GS Paper IV: Ethics, Integrity, and Aptitude

• The “Playing God” Dilemma: Gene editing technologies like CRISPR, especially when applied to the human germline (heritable changes), raise fundamental ethical questions. It challenges the concept of natural human identity and could lead to a slippery slope towards non-therapeutic enhancement (“designer babies”).
• Equity and Justice: Advanced biotechnologies are expensive and may only be accessible to the wealthy, potentially creating a new form of genetic divide between the “haves” and “have-nots,” exacerbating existing social inequalities.
• Informed Consent: The ethical principle of informed consent is complex in biotechnology. In the case of germline editing or creating a “three-parent baby,” the resulting individual cannot provide consent for modifications to their genetic makeup. In animal cloning, the issue of animal welfare and suffering for experimental purposes is a major ethical concern.
• Precautionary Principle: Given the potential for irreversible changes to the gene pool and ecosystems, the precautionary principle should be a guiding tenet in the regulation of biotechnology. This means taking proactive measures to prevent harm even when scientific certainty is lacking.

GS Paper I: Indian Society

• Impact on Social Structures: Technologies like the three-parent baby challenge traditional definitions of parentage and kinship. The legal and social recognition of a child with three genetic parents needs careful consideration.
• Farmer Suicides and Agrarian Distress: The debate around GM crops is intrinsically linked to the agrarian crisis. The high cost of patented GM seeds and associated inputs can increase farmer indebtedness if crops fail, highlighting the need for technologies that are not only effective but also economically sustainable for small and marginal farmers.

GS Paper II: Governance

• Need for Robust Legislation: India’s legal framework for biotechnology is fragmented across several acts (e.g., Biological Diversity Act, Food Safety & Standards Act). There is a need for a comprehensive and updated legislative framework that can effectively govern the rapid advancements in this field, addressing both biosafety and ethical concerns.
• Role of Institutions: Strengthening scientific and regulatory institutions like GEAC, ensuring their autonomy, and promoting public engagement are crucial for building trust and making informed decisions on the adoption of biotechnologies. International collaboration and harmonizing regulatory standards are also essential in a globalized world.