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:

The correct answer is B. Statements 2 and 3 are right, and statement 1 is wrong.

• Statement 1 (false): Stem cells are not confined to mammals. Plants have meristematic stem cells at root and shoot tips, which is the basis of plant tissue culture, and many non-mammalian animals have stem cells that renew tissues. The word "only" is the giveaway.
• Statement 2 (true): Human pluripotent and induced pluripotent stem cells are differentiated into tissue models on which new drugs are tested for efficacy and toxicity before human trials. This reduces cost and animal testing.
• Statement 3 (true): Haematopoietic stem cell transplantation is an established therapy for leukaemia and some blood disorders, and research continues for other conditions.

Core concept: stem cells are undifferentiated cells that self-renew and differentiate into specialised cells. For Mains, link this to the ethics of embryonic stem cell research and the national framework (ICMR and DBT's National Guidelines for Stem Cell Research, 2017), which restricts unproven commercial stem cell therapy.

Trap: aspirants reject statement 2 or 3 because they associate stem cells only with controversy, or they accept statement 1 without checking the plant kingdom.