Q50. The two defining properties of a stem cell are:
[SSC CHSL — Practice]
- (a) Production of haemoglobin and chlorophyll
- (b) Self-renewal and capacity to differentiate
- (c) Permanent inability to divide and no nucleus
- (d) Formation of only cell walls
Answer: (b) Self-renewal and capacity to differentiate
Explanation: Stem cells can maintain their population through self-renewal and can give rise to specialised descendants. Their differentiation capacity varies: embryonic stem cells are pluripotent, whereas many adult stem cells are restricted to particular tissue lineages.
Q49. Who achieved landmark enzymatic synthesis of DNA outside living cells?
[BPSC (Pre) 2015]
- (a) Arthur Kornberg
- (b) Robert Hooke
- (c) Edward Jenner
- (d) Louis Pasteur
Answer: (a) Arthur Kornberg
Explanation: Arthur Kornberg isolated DNA polymerase and demonstrated enzymatic DNA synthesis in vitro. His research clarified mechanisms of DNA replication and earned a share of the 1959 Nobel Prize in Physiology or Medicine with Severo Ochoa.
Q48. Embryonic stem cells are traditionally isolated from which embryonic structure?
[SSC MTS — Practice]
- (a) Adult skin epidermis
- (b) Mature sperm tail
- (c) Placental villus only
- (d) Inner cell mass of the blastocyst
Answer: (d) Inner cell mass of the blastocyst
Explanation: Embryonic stem cells are classically derived from the inner cell mass of a preimplantation blastocyst. These cells can generate derivatives of the three embryonic germ layers. Their derivation and use raise important ethical and regulatory questions.
Q47. A pluripotent stem cell can produce:
[RRB NTPC — Practice]
- (a) Only red blood cells
- (b) An entire organism including all extraembryonic tissues in every setting
- (c) Cell types derived from all three embryonic germ layers
- (d) Only mature sperm cells
Answer: (c) Cell types derived from all three embryonic germ layers
Explanation: Pluripotency means the ability to differentiate into a broad range of cell types originating from ectoderm, mesoderm and endoderm. It differs from totipotency, which includes the capacity to generate extraembryonic supporting structures under suitable conditions.
Q46. Induced pluripotent stem cells are usually produced by:
[RRB Group D — Practice]
- (a) Collecting only adult erythrocytes
- (b) Reprogramming differentiated somatic cells
- (c) Fusing two sperm cells
- (d) Removing every gene from an embryo
Answer: (b) Reprogramming differentiated somatic cells
Explanation: Induced pluripotent stem cells are created by reprogramming differentiated cells using defined factors. They acquire properties resembling embryonic pluripotency. This approach supports disease modelling and drug testing while avoiding some issues linked to embryonic-cell derivation.
Q45. Apart from ordinary fingerprints, which characteristics can support biometric identification?
1. Iris patterns;
2. retinal patterns;
3. voice characteristics.
[UPSC CSE (Pre) 2014]
- (a) 1, 2 and 3
- (b) 2 and 3 only
- (c) 1 and 3 only
- (d) 1 only
Answer: (a) 1, 2 and 3
Explanation: Biometrics identifies individuals through measurable biological or behavioural characteristics. Iris texture, retinal vascular patterns and voice features can all contribute to authentication. Their reliability differs, so practical systems may combine multiple characteristics and safeguards against impersonation.
Q44. Who is especially associated with the development of induced pluripotent stem-cell technology?
[CGPSC — Practice]
- (a) Edward Jenner
- (b) Louis Pasteur
- (c) Robert Koch
- (d) Shinya Yamanaka
Answer: (d) Shinya Yamanaka
Explanation: Shinya Yamanaka and colleagues identified transcription factors that can reprogram somatic cells into induced pluripotent stem cells. The work earned Yamanaka a share of the 2012 Nobel Prize in Physiology or Medicine with John Gurdon.
Q43. Haematopoietic stem cells principally produce which cell family?
[UPSC CDS — Practice]
- (a) Plant root hairs
- (b) Neurons exclusively
- (c) Blood cells
- (d) Pancreatic digestive enzymes only
Answer: (c) Blood cells
Explanation: Haematopoietic stem cells reside mainly in bone marrow and generate red cells, white cells and platelets through differentiated precursor lineages. Stem-cell transplantation can restore blood formation after selected cancers, marrow failure and some inherited disorders.
Q42. Which source provides haematopoietic stem cells and is often collected after childbirth?
[UPSC NDA — Practice]
- (a) Mature tooth enamel
- (b) Umbilical cord blood
- (c) Hair shaft without root
- (d) Intestinal mucus alone
Answer: (b) Umbilical cord blood
Explanation: Umbilical cord blood contains blood-forming stem and progenitor cells. After birth, it may be collected and stored for potential transplantation. Its clinical usefulness depends on cell dose, donor compatibility and the condition being treated.
Q41. Recombinant DNA methods permit gene transfer:
1. between plant species;
2. from animals to plants;
3. from microorganisms to higher organisms.
[UPSC CSE (Pre) 2013]
- (a) All three
- (b) 2 and 3 only
- (c) 1 and 3 only
- (d) 1 only
Answer: (a) All three
Explanation: Recombinant DNA technology does not inherently require donor and recipient to belong to the same species. Subject to successful gene expression and biological compatibility, genetic constructs may move among plants, animals and microorganisms. Thus all three proposed transfers are possible.
