๐ Topic 04 of 6 ยท Chapter 04 ยท Biotechnology & Genetic Engineering
Stem Cells & Cloning
Embryonic, adult, iPSC stem cells, Dolly sheep, India’s policy โ complete notes for UPSC & PSC exams.
๐ฌ Types of Stem Cells
| Type | Source | Potential | Controversy |
|---|---|---|---|
| Embryonic Stem Cells (ESCs) | Early embryo (blastocyst, 5-7 days old) | Pluripotent โ can become ANY cell type | High โ destroys embryo; ethical concerns |
| Adult Stem Cells | Bone marrow, blood, skin, brain | Multipotent โ limited cell types | Low โ no embryo destruction |
| iPSCs (Induced Pluripotent Stem Cells) | Adult cells reprogrammed to embryonic-like state | Pluripotent โ like ESCs | Low โ no embryo needed; Nobel Prize 2012 |
| Cord Blood Stem Cells | Umbilical cord blood at birth | Multipotent | Low โ collected at birth |
๐ฌ iPSCs โ Nobel Prize 2012
- Nobel Prize in Physiology or Medicine 2012 โ Shinya Yamanaka (Japan) and John Gurdon (UK)
- Yamanaka showed adult mouse skin cells can be reprogrammed into pluripotent stem cells by introducing just 4 genes (Oct4, Sox2, Klf4, c-Myc)
- iPSCs behave like embryonic stem cells but avoid ethical controversy
- Can be made from patient’s own cells โ no immune rejection
- Applications: personalised medicine, drug testing, disease modelling
๐ Cloning โ Dolly the Sheep
- Dolly the sheep (1996) = first mammal cloned from an adult somatic cell
- Created by Ian Wilmut and colleagues at Roslin Institute, Scotland
- Method: Somatic Cell Nuclear Transfer (SCNT) โ nucleus from adult cell inserted into enucleated egg cell
- Dolly lived for 6 years (died 2003); had premature aging
- Proved adult cells retain all genetic information needed to create a new organism
- Therapeutic cloning = cloning to produce stem cells for medical treatment (not reproductive)
- Reproductive cloning = cloning to produce a new organism = banned in most countries
โญ Key Facts:
โข Dolly the sheep (1996) = first cloned mammal = Roslin Institute, Scotland
โข iPSCs = Nobel Prize 2012 = Shinya Yamanaka + John Gurdon
โข ESCs = pluripotent = from embryo = ethical controversy
โข Adult stem cells = multipotent = bone marrow = no controversy
โข India’s stem cell policy = allows research on embryonic stem cells with restrictions
โข Dolly the sheep (1996) = first cloned mammal = Roslin Institute, Scotland
โข iPSCs = Nobel Prize 2012 = Shinya Yamanaka + John Gurdon
โข ESCs = pluripotent = from embryo = ethical controversy
โข Adult stem cells = multipotent = bone marrow = no controversy
โข India’s stem cell policy = allows research on embryonic stem cells with restrictions