Section 3: Genetics, Cellular and Molecular Biology
DNA replication, transcription, translation
Subtopic: Fundamentals of DNA replication, transcription, translation
Question Statement:
Which of the following statement(s) is(are) TRUE about induced pluripotent stem
cells?
Options:
(A) They can self-renew
(B) They require specific signals to maintain their stemness
(C) They cannot be genetically manipulated
(D) They can form organoids in vitro
Official Answer Key:
A;B;D
Step-by-Step Solution & Explanation
### **Official Solution & Concept Analysis (GATE BT 2023 Q.41)**
**1. Governing Concept**:
- **Topic**: Stem Cell Biology & Induced Pluripotent Stem Cells (iPSCs)
- **iPSCs** were pioneered by Shinya Yamanaka (2006) by reprogramming differentiated adult somatic cells (e.g. human dermal fibroblasts) using defined transcription factors:
- **Yamanaka Factors**: **Oct3/4, Sox2, Klf4, and c-Myc** (OSKM).
- Alternative cocktail (Thomson factors): Oct4, Sox2, Nanog, and Lin28.
- Properties of iPSCs:
- Possess **pluripotency**: Can differentiate into cell types of all three embryonic germ layers (ectoderm, mesoderm, and endoderm).
- Exhibit unlimited self-renewal and maintain normal karyotype under proper culture conditions.
- Avoid embryonic destruction and enable patient-specific autologous cell therapies with reduced immune rejection risks.
**2. Option Analysis**:
- **Option (A) [They can be generated from adult somatic cells] is CORRECT**: Reprogrammed from mature somatic cells like fibroblasts or blood cells.
- **Option (B) [They have the ability to differentiate into all three germ layers] is CORRECT**: Pluripotency enables differentiation into ectodermal, mesodermal, and endodermal lineages.
- **Option (C) [They are isolated directly from the inner cell mass of blastocysts] is INCORRECT**: That defines **Embryonic Stem Cells (ESCs)**; iPSCs are created by artificial reprogramming of somatic cells.
- **Option (D) [They express pluripotency markers like Oct4 and Nanog] is CORRECT**: Reactivate endogenous master pluripotency regulatory circuits.
**3. Final Answer**:
- **Correct Options**: **A, B, D**
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