Cell Biology: Organelles, iPSC Technology & MRT

UPSC Mains PYQs

Stem Cells & Therapeutics (2020): Explain the concept of stem cells and discuss their potential applications in regenerative medicine and therapeutic cloning. (10 Marks, 150 Words)

📊 High-Yield Data & Statistical Fact Sheet

Cellular & Stem Cell Metrics:
- Mitochondrial Burden: Mitochondrial disorders affect 1 in 5,000 live births globally, caused by defects in maternally inherited mitochondrial DNA (mtDNA).
- mtDNA Parameters: Mitochondria carry 16,569 base pairs encoding 37 genes (~0.1% of total human genetic material), entirely inherited from the mother.
- ICMR 2017 Guidelines: Prohibits commercial banking of cord tissue, placenta, or deciduous teeth; permits only Hematopoietic Stem Cell (HSC) banking for blood disorders.
- Yamanaka Factors: iPSC reprogramming is achieved using 4 specific transcription factors (Oct3/4, Sox2, Klf4, c-Myc) to turn adult somatic cells pluripotent.
- Apoptosis Rate: A healthy human adult replaces 50 to 70 Billion cells daily via programmed cell death.
- Hayflick Limit: Normal somatic cells divide 40 to 60 times before reaching senescence due to telomeric decay.

1. CELL ORGANELLES & MITOCHONDRIAL GENOMICS

Key Cellular Organelles:
- Nucleus: Houses the master double-stranded nuclear DNA template governing cellular operations.
- Ribosomes: The protein translation factories; key target sites for many clinical antibiotics.
- Lysosomes: The waste recycling centers of the cell; degradation failures lead to neurodegenerative diseases.
Mitochondrial DNA (mtDNA): Organelles containing their own autonomous, circular DNA, which is inherited entirely from the mother.
Mitochondrial Replacement Therapy (MRT): A three-parent IVF technique designed to prevent transmission of severe genetic mitochondrial diseases. Includes Maternal Spindle Transfer (MST) or Pronuclear Transfer (PNT), substituting mutant maternal mitochondria with healthy donor mitochondria.

Stem Cell Potency Gradients:
- Totipotency: Can form an entire organism, including embryonic and extra-embryonic tissues (e.g., zygote).
- Pluripotency: Can differentiate into any of the three embryonic germ layers (endoderm, mesoderm, ectoderm) to form any somatic cell type (e.g., Embryonic Stem Cells).
- Multipotency: Can differentiate into a limited range of cell lineages (e.g., Hematopoietic stem cells).
Induced Pluripotent Stem Cells (iPSC): Somatic adult cells (e.g., skin cells) genetically reprogrammed back to an embryonic pluripotent state using the 4 Yamanaka factors.
Therapeutic Advantages: iPSCs bypass the ethical concerns of destroying human blastocysts and eliminate the risk of immunological rejection, as patient-derived cells are used.

Apoptosis (Programmed Cell Death): Controlled cellular self-destruction that eliminates damaged or pre-cancerous cells. Dysfunction leads to uncontrolled tumor growth.
Autophagy: The cellular self-eating recycling process where cells digest their own damaged organelles via lysosomes to survive nutrient starvation and clear toxic proteins.
National Guidelines for Stem Cell Research 2017: Joint ICMR-DBT framework:
- Approved: Hematopoietic Stem Cell Transplantation (HSCT) for blood-related disorders (leukemias, thalassemias).
- Prohibited: Human germline gene editing, reproductive cloning, and commercial banking of unproven stem cells (cord tissue, placenta).

Maternal Inheritance Organelle: Mitochondria.
Three-Parent IVF Technologies: MST (Maternal Spindle Transfer) & PNT (Pronuclear Transfer).
Universal Energy Organelle Genes: 37 genes (mtDNA).
Reprogrammed Somatic Cells: iPSC (Induced Pluripotent Stem Cells).
iPSC Reprogramming factors: Yamanaka Factors (4 transcription factors).
Programmed Cell Death term: Apoptosis.
Cell Self-Eating Process: Autophagy (Ohsumi Nobel 2016).
Approved Indian Stem Cell Therapy: HSCT (Hematopoietic Stem Cell Transplantation).

Notes updated up to March 2026. Sources: ICMR Stem Cell Guidelines, Nature Cell Biology Review.