Assertion (A) : Dolly was the first cloned mammal. Reason (R) : Dolly was produced by in vitro fertilization.

Assertion (A) is essentially true in the intended exam sense: Dolly was the landmark cloned sheep—famously the first mammal cloned from a differentiated adult somatic cell and announced in 1997, marking a major breakthrough in reproductive cloning [3]. Reason (R) is false: Dolly was not produced by in vitro fertilization. Instead, Roslin scientists used somatic cell nuclear transfer (SCNT), transferring the nucleus from an adult mammary-cell donor into an enucleated egg, stimulating it to divide and implanting the resulting embryo into a surrogate mother [3]. Thus A is true (in context) but R incorrectly attributes the method to IVF rather than SCNT [2].

Sources

1. [2] https://hms.harvard.edu/news/improving-cloning-efficiency
2. [3] https://www.nms.ac.uk/discover-catalogue/the-story-of-dolly-the-sheep
3. [1] https://ourhistory.is.ed.ac.uk/index.php/Cloning_of_Dolly_the_Sheep%2C_1996