With reference to the latest developments in stem cell research, consider the following statements: 1. The only source of human stem cells are the embryos at blastocyst stage 2. The stem cells can be derived a without causing destruction to blastocysts 3. The stem cells can regenerate themselves in vitro virtually forever 4. Indian research centres also created a few cell lines which can be developed into many types of tissues Which of these statements are correct?

The correct answer is D because only statements 3 and 4 are scientifically accurate. Statement 1 is incorrect because embryos are not the only source of human stem cells. They can also be found in adult tissues like bone marrow, skin, and umbilical cord blood. Furthermore, induced pluripotent stem cells can be created by reprogramming adult cells. Statement 2 is incorrect because the traditional method of extracting embryonic stem cells involves the destruction of the blastocyst. While newer techniques like single cell biopsy have been explored, they are not the standard or primary method associated with general stem cell research developments cited in this context. Statement 3 is correct because stem cells possess the unique property of self renewal. In a controlled laboratory environment or in vitro, they can divide and replicate themselves indefinitely while maintaining their unspecialized state. Statement 4 is correct because Indian institutions, such as the National Centre for Biological Sciences and various private research facilities, have successfully developed several embryonic stem cell lines that are capable of differentiating into various tissue types.