With reference to ‘stem cells’, frequently in the news, which of the following statements is/are correct? 1. Stem cells can be derived from mammals only. 2. Stem cells can be used for screening new drugs. 3. Stem cells can be used for medical therapies. Select the correct answer using the codes given below :

1. Basics of Cell Differentiation and Potency (basic)

Every complex multicellular organism, including humans, begins its journey as a single cell. However, a single cell type cannot perform all the tasks required for life. To solve this, nature uses a process called Cell Differentiation. This is the transformation of a generic, 'unspecialized' cell into a highly specialized one with a specific shape and function. For instance, a muscle cell develops a spindle shape and special proteins to allow for contraction, while a nerve cell becomes long and branched to transmit electrical impulses across the body Science, Class VIII, The Invisible Living World: Beyond Our Naked Eye, p.13 Science, class X, Control and Coordination, p.105. Once a cell is 'fully differentiated,' it has essentially 'chosen its career' and usually loses the ability to become a different type of cell.

Before a cell differentiates, it possesses Potency—which is its 'potential' or capacity to turn into other cell types. In the early stages of life, there must be a single cell type capable of growing, proliferating, and generating all other cell types under the right circumstances Science, class X, How do Organisms Reproduce?, p.116. This concept isn't limited to embryos. Some organisms, like Hydra and Planaria, maintain pockets of these 'potent' cells throughout their lives. If these animals are cut into pieces, these specialized cells proliferate to create a mass of new cells, which then differentiate into various tissues to regrow the entire organism—a remarkable feat known as regeneration Science, class X, How do Organisms Reproduce?, p.116.

Feature	Undifferentiated Cell (High Potency)	Differentiated Cell (Specialized)
Function	General; primary role is to divide and produce other cells.	Specific; e.g., carrying oxygen, transmitting signals, or contraction.
Structure	Simple, often round or generic.	Unique shapes (e.g., long branches in nerve cells).
Potential	High; can become many different cell types.	Low; fixed in its specific identity.

Sources: Science, Class VIII (Revised ed 2025), The Invisible Living World: Beyond Our Naked Eye, p.13; Science, class X (NCERT 2025 ed.), Control and Coordination, p.105; Science, class X (NCERT 2025 ed.), How do Organisms Reproduce?, p.116

2. Natural Regeneration Across Species (basic)

Regeneration is a fascinating biological process where many fully differentiated organisms possess the ability to give rise to new individuals from their own body parts. In simple terms, if an organism is cut or broken into pieces, those fragments can grow back into complete, independent individuals. This is not a random occurrence but a highly organized cellular event. For instance, simple animals like Hydra and Planaria (a type of flatworm) exhibit this remarkable capability Science, Class X (NCERT 2025 ed.), Chapter 7, p.116.

At the heart of regeneration are specialized cells. When an injury or fragmentation occurs, these cells do not just sit idle; they begin to proliferate, meaning they divide rapidly to create a large mass of cells. From this cluster, different cells undergo specific changes to become various cell types and tissues, effectively rebuilding the missing parts of the body Science, Class X (NCERT 2025 ed.), Chapter 7, p.116. Scientists study organisms like Planaria specifically to unlock the secrets of how these cells "know" how to regrow a whole body from a mere fragment Science, Class VIII (NCERT Revised ed 2025), p.221.

It is important to distinguish regeneration from other forms of growth. In many simple organisms, regeneration serves as a mode of asexual reproduction, where a single individual can create a new generation without the need for a partner Science, Class X (NCERT 2025 ed.), Chapter 7, p.119. In Hydra, these regenerative cells are also used for budding, where a small outgrowth (bud) develops due to repeated cell division at one site, eventually detaching to become a new individual Science, Class X (NCERT 2025 ed.), Chapter 7, p.117.

Feature	Regeneration	Budding
Mechanism	Regrowth from broken/cut body fragments.	Development of an outgrowth (bud) at a specific site.
Cell Type	Specialized regenerative cells.	Repeated cell division of regenerative cells.
Example	Planaria, Hydra.	Hydra, Yeast.

Sources: Science, Class X (NCERT 2025 ed.), Chapter 7: How do Organisms Reproduce?, p.116, 117, 119; Science, Class VIII (NCERT Revised ed 2025), Our Home: Earth, a Unique Life Sustaining Planet, p.221

3. Types of Stem Cells: Embryonic vs. Adult (intermediate)

At their core, stem cells are the body’s raw materials — undifferentiated 'master cells' from which all other cells with specialized functions are generated. Under the right conditions, these cells divide to form more cells called daughter cells. These daughter cells either become new stem cells (self-renewal) or become specialized cells (differentiation) with a specific function, such as blood cells, brain cells, or muscle cells Science, Class VIII NCERT, The Invisible Living World, p.13. While we often think of stem cells in a human context, they are a fundamental feature of multicellular life; for instance, simple organisms like Hydra and Planaria possess specialized regenerative cells that allow them to regrow entire body parts if they are cut Science, Class X NCERT, How do Organisms Reproduce?, p.116.

The two primary categories we study are Embryonic Stem Cells (ESCs) and Adult (Somatic) Stem Cells. ESCs are derived from embryos that are three to five days old (a stage called a blastocyst). These cells are pluripotent, meaning they have the incredible potential to turn into any cell type in the body. In contrast, Adult Stem Cells are found in small numbers in most adult tissues, such as bone marrow or fat. They are typically multipotent, meaning their ability to differentiate is limited to the family of cells from which they originate (e.g., bone marrow stem cells primarily create blood cells).

Understanding the differences between these two is crucial for medical science and ethics:

Feature	Embryonic Stem Cells (ESCs)	Adult Stem Cells
Potency	Pluripotent: Can become any cell type in the body.	Multipotent: Limited to specific lineages (e.g., blood, skin).
Source	Inner cell mass of a blastocyst.	Specific tissues (bone marrow, brain, liver, skin).
Growth Potential	Can be grown relatively easily in culture.	Difficult to isolate and grow in large quantities.
Ethical Status	High controversy due to the destruction of embryos.	Generally considered ethically neutral.

Beyond therapy, stem cells serve as vital tools for the pharmaceutical industry. Before testing new drugs on humans, scientists use stem cells to create specific tissue models (like 'mini-hearts' or 'mini-livers') to screen for drug toxicity and effectiveness. This in vitro testing reduces risk and accelerates the development of safe medicines.

Sources: Science, Class X NCERT, How do Organisms Reproduce?, p.116; Science, Class VIII NCERT, The Invisible Living World: Beyond Our Naked Eye, p.13

4. Genetic Engineering and Gene Therapy (intermediate)

Concept: Genetic Engineering and Gene Therapy

5. Biotechnology Regulations and Ethics in India (exam-level)

In India, biotechnology and stem cell research are governed by a robust, multi-layered regulatory framework designed to balance scientific progress with ethical safeguards. The primary architects of these regulations are the Department of Biotechnology (DBT) and the Indian Council of Medical Research (ICMR). At the heart of stem cell oversight are the National Guidelines for Stem Cell Research (2017), which mandate that all research must be ethical, transparent, and scientifically sound. Because a single cell has the remarkable potential to proliferate and differentiate into diverse cell types Science, Class X (NCERT 2025 ed.), How do Organisms Reproduce?, p.116, the government strictly categorizes research into Permissible, Restricted, and Prohibited areas to prevent misuse.

The regulatory architecture operates at two main levels: institutional and national. Every organization involved in stem cell research must establish an Institutional Committee for Stem Cell Research (IC-SCR) to provide internal oversight. At the national level, the National Apex Committee for Stem Cell Research and Therapy (NAC-SCRT) monitors high-stakes research and sets policy. Furthermore, for any clinical trial or commercial application involving stem cells, approval from the Central Drugs Standard Control Organization (CDSCO) is mandatory, as stem cells are classified as 'Investigational New Drugs' in India.

Ethically, India maintains a strict stance on sensitive issues. While the use of adult stem cells and umbilical cord blood is generally encouraged for therapeutic research, the creation of human embryos solely for research is highly restricted. Certain practices are strictly prohibited, including human cloning (reproductive cloning), germline gene therapy (which affects future generations), and the in vitro culture of intact human embryos beyond 14 days. These boundaries ensure that India's biotech sector, supported by institutions like the National Institute of Immunology (NII) and the Centre for DNA Fingerprinting and Diagnostics (CDFD) Environment and Ecology, Majid Hussain, Major Crops and Cropping Patterns in India, p.82, remains aligned with international ethical standards.

Category	Examples	Status
Permissible	Adult stem cells, established hESC lines, cord blood.	Allowed with IC-SCR approval.
Restricted	Creation of new hESC lines, chimera research.	Requires NAC-SCRT clearance.
Prohibited	Human reproductive cloning, germline modification.	Strictly banned in India.

Sources: Science, Class X (NCERT 2025 ed.), How do Organisms Reproduce?, p.116; Environment and Ecology, Majid Hussain, Major Crops and Cropping Patterns in India, p.82

6. Induced Pluripotent Stem Cells (iPSCs) and Drug Screening (exam-level)

Induced Pluripotent Stem Cells (iPSCs) represent a revolutionary leap in biotechnology. Unlike embryonic stem cells, which are harvested from embryos, iPSCs are created by reprogramming mature adult cells (such as skin or blood cells) back into a pluripotent state. This means they regain the ability to become almost any cell type in the human body. In the context of pharmaceutical research, this provides a 'limitless' supply of human cells—such as neurons or cardiac cells—that carry the exact genetic signature of a patient, allowing for personalized drug testing without the ethical concerns associated with embryonic tissue. Traditionally, new drugs are tested for safety and efficacy using animal models like mice, rats, and dogs to establish toxicity levels, such as the LD 50 (the dose required to kill 50% of a test population) Environment, Shankar IAS Academy, Environment Issues and Health Effects, p.415. However, animal biology often differs significantly from human biology, leading to high failure rates in human clinical trials. iPSCs bridge this gap by allowing scientists to conduct 'In Vitro' (in a lab dish) screening on actual human cells. This ensures that the physiological response observed is human-specific, significantly increasing the predictive power of the test before a drug ever reaches a human volunteer. Furthermore, iPSCs enable the creation of 'Disease-in-a-Dish' models. For instance, if a drug is being developed for Parkinson’s disease—a condition characterized by jerky movements—scientists can derive iPSCs from a Parkinson's patient, turn them into dopamine-producing neurons, and test potential treatments like L-Dopa or newer candidates directly on those diseased cells Environment and Ecology, Majid Hussain, Major Crops and Cropping Patterns in India, p.90. This helps identify which chemical compounds are effective and which might cause dangerous side effects, such as heart arrhythmia or liver damage, long before the drug is manufactured for the public.

Sources: Environment, Shankar IAS Academy, Environment Issues and Health Effects, p.415; Environment and Ecology, Majid Hussain, Major Crops and Cropping Patterns in India, p.90

7. Modern Medical Applications: Regenerative Medicine (exam-level)

Regenerative Medicine is a transformative branch of healthcare that seeks to "repair, replace, or regenerate" damaged human cells, tissues, and organs. While traditional medicine often manages symptoms using external chemicals, regenerative medicine harnesses the body’s own biological toolkit to fix the root cause of a disease. At the heart of this field are Stem Cells—master cells capable of proliferating and maturing into specialized cell types under the right conditions Science, Class X (NCERT 2025 ed.), How do Organisms Reproduce?, p.116. Since all living beings are fundamentally composed of cells Science, Class VIII (NCERT 2025 ed.), The Invisible Living World, p.10, controlling these units allows us to potentially reverse conditions previously thought to be permanent.

One of the most profound applications is in treating Central Nervous System (CNS) injuries. The brain and spinal cord serve as the body's main coordinating centers Science, Class X (NCERT 2025 ed.), Control and Coordination, p.103, but they have a very limited capacity to heal themselves. When a spinal cord injury occurs, vital signals between the brain and the rest of the body are disrupted Science, Class X (NCERT 2025 ed.), Control and Coordination, p.112. Regenerative therapies aim to transplant stem cells into the site of injury to regrow neural connections, effectively "rewiring" the damaged communication lines. Similarly, this technology is used in Bone Marrow Transplants to treat blood cancers like leukemia and is being explored to create insulin-producing cells for diabetic patients.

Beyond direct therapy, regenerative medicine has revolutionized Pharmacology and Drug Discovery. Instead of relying solely on animal models, scientists use Induced Pluripotent Stem Cells (iPSCs) to grow human tissues in vitro (in a lab setting). These lab-grown tissues allow researchers to perform toxicity assessments and screen new drug candidates with high precision. By observing how a new drug affects human heart or liver cells in a dish, we can ensure safety long before a human volunteer ever takes a dose.

Sources: Science, Class X (NCERT 2025 ed.), How do Organisms Reproduce?, p.116; Science, Class VIII (NCERT 2025 ed.), The Invisible Living World: Beyond Our Naked Eye, p.10; Science, Class X (NCERT 2025 ed.), Control and Coordination, p.103, 112

8. Solving the Original PYQ (exam-level)

Now that you have mastered the fundamental properties of stem cells—specifically their capacity for self-renewal and potency—you can see how these building blocks form the logic of this question. The core concept is that because these cells are undifferentiated, they act as a biological repair kit. As highlighted in Science, Class X (NCERT 2025 ed.), the process of regeneration in various organisms relies on these specialized cells to proliferate and transform into different cell types. This versatility is exactly what makes them useful for both medical therapies (replacing damaged tissue) and drug screening (testing toxicity on human-like cells in a lab).

To arrive at the correct answer, (B) 2 and 3 only, we must evaluate the practical applications of biotechnology. Think of statement 2 as a safety filter: using stem cells, particularly induced pluripotent stem cells (iPSCs), allows scientists to observe how a new drug reacts with human-like tissue before it ever touches a patient. Similarly, statement 3 is the primary goal of regenerative medicine. Whether it is a bone marrow transplant for leukemia or experimental treatments for diabetes, the ability to grow new, healthy cells is the foundation of modern stem cell therapy, a fact reinforced by recent research in Nature (2025).

The common UPSC trap is found in Statement 1. Watch out for extreme qualifiers like "only," "all," or "always," which are frequently used to make a statement false. While we often focus on human stem cells in the news, they are not exclusive to mammals. Simple multicellular organisms like Hydra and Planaria possess incredible regenerative powers due to their own versions of stem cells, as noted in NCERT Chapter 7. By identifying this over-generalization, you can confidently eliminate Statement 1 and conclude that only the functional applications (2 and 3) are correct.