Correct Option
Dolly the sheep was successfully cloned in 1996 by the Roslin Institute in Scotland. This event marked the first successful cloning of a mammal from an adult somatic cell, demonstrating that a specialized adult cell could be reprogrammed to create an entire organism. Therefore, Assertion (A) is true.
However, Dolly was not produced by in vitro fertilization (IVF). IVF involves the fertilization of an egg by sperm outside the body. Instead, Dolly was created using the technique of Somatic Cell Nuclear Transfer (SCNT). This process involves transferring the nucleus from an adult somatic cell into an enucleated egg cell, which is then stimulated to develop into an embryo and implanted into a surrogate mother. Consequently, Reason (R) is false.
Since Assertion (A) is true and Reason (R) is false, option (3) is the correct answer.
Incorrect Options
Options (1) and (2) are incorrect because they both state that Reason (R) is true, which is factually inaccurate. Dolly was produced by Somatic Cell Nuclear Transfer (SCNT), not in vitro fertilization.
Option (4) is incorrect because it states that Assertion (A) is false. Dolly was indeed the first mammal cloned from an adult somatic cell, making the assertion true.