Describe how a plasmid can be genetically modified to in clude a piece of foreign dna that alters the phenotype of bacterial cells transformed with the modified plasmid. describe a procedure to determine which bacterial cells have been successfully transformed.

A plasmid is a circular DNA found in bacterial.A plasmid can be modified into another through a process called genetic engineering. In this mechanism, a plasmid is taken from one bacterial into another bacteria. the enzyme used in this process is called restriction enzyme ( found naturally in bacterials), to begin, we first isolate the gene we are using from it's host, then the plasmid is removed and they are joined together. now the plasmid has part it's own and a foreign DNA. they then multiply and produce more of the target cells. a typical example is human and insulin production as described below 

in the past, people with diabetes have not been able to produce enough insulin protein. insulin from cows and pigs have been used to treat diabetes through this process of genetic engineering.