Final answer:
The answer is b) Ends. Source and vector DNA cut with the same restriction enzyme create complementary sticky ends, which can be sealed by DNA ligase to form recombinant DNA.
Step-by-step explanation:
The correct answer to the student's question is b) Ends. When source and vector DNA are cut with the same restriction enzyme, they produce complementary ends that can base pair with each other. These ends are also known as sticky ends because they can form hydrogen bonds with complementary sticky ends of another piece of DNA cut by the same restriction enzyme. The enzyme DNA ligase is then used to seal the bonded ends, creating recombinant DNA through a process known as ligation.
Overall, the steps involved in the formation of recombinant DNA involve cutting both DNA molecules with the same restriction enzyme to create complementary sticky ends, annealing these ends through base-pairing, and sealing them using DNA ligase to form the continuous DNA strand. This technique is fundamental in the field of genetic engineering, allowing researchers to insert genes and form new genetic combinations.