Ligation is a medical procedure that involves tying off a blood vessel or duct to prevent blood flow or the passage of fluids. This technique is often used in surgeries to control bleeding or to isolate a specific area of the body. It can also be applied in various medical treatments, such as in the removal of tumors or in contraceptive methods like tubal ligation. In addition to its surgical applications, ligation is also used in molecular biology. Here, it refers to the process of joining two strands of DNA together, often using enzymes called ligases. This technique is crucial for cloning and genetic engineering, allowing scientists to create recombinant DNA for research and therapeutic purposes.