Assertion (A) : Scientists can cut apart and paste together DNA molecules at will, regardless of the source of the molecules. Reason (R) : DNA fragments can be manipulated using restriction endonucleases and DNA ligases.

Both the assertion and reason are true, and the reason correctly explains the assertion. Recombinant DNA technology allows joining DNA segments from different sources to create new genetic constructs; inserting foreign genes into organisms is a defining feature of genetic modification [1]. The practical basis for this capability is the pair of enzymatic tools: restriction endonucleases (which make precise cuts at specific recognition sequences) and DNA ligases (which join DNA fragments together). These enzymes were central to the first recombinant‑DNA experiments and remain the backbone of molecular cloning workflows, enabling scientists to ‘cut and paste’ DNA in vitro and assemble constructs for propagation in cells [2].

Sources

1. [1] Indian Economy, Nitin Singhania .(ed 2nd 2021-22) > Chapter 9: Agriculture > GENETICALLY MODIFIED (GM) CROPS > p. 301
2. [2] https://www.science.org/doi/10.1126/sciadv.adj8277