Question

Why do you think plasmids and bacterial cells are such important tools in genetic engineering

Answer 1

Wow, that's quite a coincidence. I was just studying for my molecular biology test tomorrow.
Plasmids are vectors which you can cut on 1 place with restriction-endonuclease enzymes. Then you can insert a fragment of DNA and "paste" it in the vector using DNA ligase. Next you transform the plasmid with the recombinant DNA in a bacterial cell to multiply your fragment in the vector plasmid a million times. Then you can either use the bacterial colonies for antibiotic resistance experiments or lyse the cells to extract the DNA and use it for electrophoresis. That way you can determine the nucleobase-lengths of the different fragments.

For example you can insert the human insulin-coding gene in a vector plasmid and transform it in a bacterial cell. then you let the cells grow. the cells with a plasmid containing the insulin gene will produce insulin which you can later extract from the medium. That way we can produce insulin without the need of a pancreas and that's very useful for diabetics.