Microbes and Genetic Engineering

How Does It Work?

Brief History
How Does It Work?
WebMicro 2000
7 Basic Steps

In order to understand genetic engineering, you need to be familiar with certain terminology and processes. There are slightly different methods that can be used to put together DNA from different organisms. This page focuses on creating genetically engineered bacteria. For example, if a scientist knows that gene in humans that makes the enzyme which breaks down dairy products. Scientists may want copies of this gene to treat people who get sick from dairy products because these can't make this enzyme. Scientists would want to collect copies of this gene from people or make copies by reactions in a laboratory. This gene could then be transferred to bacteria. The bacteria can then make the human enzyme because they now have human DNA in their cells. The following is a simplified explanation of the general procedures that would be used to produce a genetically engineered bacterial cell. There are links to additonal information that may help clarify concepts for those who become confused. There are also links that provide more details for those who want further information on the basic procedures.  

Step 1: A gene is picked that controls a trait in which scientists are interested. DNA containing that gene is collected from the donor organism that naturally has this gene. Scientists can also make copies of the DNA in a laboratory if they don't have a lot of it.

Step 2: Scientists isolate plasmid DNA (a ring of DNA in a bacterial cell) from bacteria. This ring of DNA will carry the gene to the new organism. The plasmid will serve as a vector.

Step 3: The donor DNA and the plasmid DNA are mixed with an enzyme (a molecule that will cause a reaction). This enzyme cuts both kinds of DNA into pieces at special spots along their code. The pieces that are left are able to easily join to each other based on their chemistry. You can think of it like puzzle pieces that fit together.

Step 4: The pieces of DNA that have matching shapes or chemistry join together to make a complete plasmid (ring of DNA). This plasmid is now a ring of DNA that has a new gene as part of the ring. This new gene is the gene that scientists chose in Step One to collect from a donor organism.

Step 5: The plasmids containing the new gene are mixed with other bacterial cells. Some of these bacteria will take the plasmids into their cells by a process called transformation. The plasmid will now be inside of these bacterial cells. These cells now all have the chosen gene inside of them. The cells containing the gene are identified and separated from the rest.

Step 6: Colonies of bacteria that contain the chosen gene or who can produce the desirable product are identified and separated.

Step 7: The genetically engineered bacteria are grown in large amounts. The product of the chosen gene can then be collected from the bacteria.

Example of the Entire Process:

Other Examples:




© 2000 Jody Becker, Robin Norwood and Brad Greenspan. All Rights Reserved, except for the images, which retain their own copyrights.
This site was designed by Jody Becker, Robin Norwood and Brad Greenspan for MBI 699.W in August of 2000.