Explain why scientists must use only certain enzymes when
inserting or removing a defective gene from a cell

Certain enzymes will splice out only the target gene and different enzymes will cut DNA at different locations.

Explanation:

Removing or inserting defective genes and replacing the defective one with the normal one is one of the genetic engineering technique that helps in curing the disease and improving the health status.

When inserting or removing any defective gene, we have to be careful in using the enzymes that would help in splicing out only the targeted gene. If wrong enzymes are used there are chances that it may cut out the normal gene.

Initially, the gene that has to be modified or removed or inserted is chosen and then it is isolated in a matching vector. Finally, it is inserted or removed from the host cell.

cell division is not regulated in tumor cells.

i'm thinking 600 feet deep in one of the finger lakes.