Hypothetical Situation

Genes that produce chlorophyll in plants are inserted into the chromosomes of cattle.

What are some of the advantages of this procedure?

The result would be an animal that is capable of making its own food.

Can you think of the potential benefits of this kind of research?

DNA Recombination

a.k.a. Gene Splicing

What is it?

Recombinant DNA refers to a new combination of DNA molecules that are not found together naturally.

Produced by joining DNA molecules from different biological sources.

The hybrid DNA is then inserted into a host cell, often a bacterium, for replication.

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Tools Needed

Restriction enzymes (biological scissors) "cut" DNA at a specific location.

DNA ligase (DNA glue) is used to "glue" two sections of DNA together.

Plasmids…

Recombinant DNA is often created using a plasmid.

Plasmids are DNA structures in bacteria

http://faculty.abe.ufl.edu/~chyn/age2062/lect/lect_09/FG10_001.GIF http://www.microbeworld.org/microbes/virus_bacterium.aspx

… or Viruses

The DNA in a virus can also be used for creating recombinant DNA

The virus can enter another cell and have its genetic code replicated by that cell

http://www.microbeworld.org/microbes/virus_bacterium.aspx

Products of Recombinant DNA Technology

Some examples of recombinant DNA products include insulin and growth hormone.

Vaccines can also be produced using recombinant DNA technology.

Step by Step…

Let’s look at the process of DNA recombination…

Step 1: A restriction enzyme is used to cut a specific DNA strand from the DNA of a cell

Step 2: The cut DNA strand is inserted into a virus.

Step 3: The virus is inserted into a cell

Step 4: The cell passes the foreign gene on to all daughter cells

A Close-up View of DNA insertion into a plasmid

Areas Where Recombinant DNA will have an Impact

Better Crops (drought & heat resistance) Recombinant Vaccines (ie. Hepatitis B) Prevention and cure of sickle cell anemia Prevention and cure of cystic fibrosis Production of clotting factors Production of insulin Plants that produce their own insecticides Gene therapy

Connections to the World Around Us

http://static.howstuffworks.com/gif/photocopier-xerox.jpg

Activity:

Make your own recombinant DNA!!

Impact of Recombinant DNA Improved Medicines Improved Livestock (resistance to

disease) Improved Crops (resistance to

disease, higher yields) Prevention of Genetic Diseases Lowering the cost of medicines

(i.e. Insulin) Safer Medicines (i.e. Insulin) Treatment for pre-existing

conditions (i.e. Cancer)

Safety concerns (viruses developing antibiotic resistance)

Environmental concerns (developing resistance to fungi)

Ethical dilemmas over human treatment (i.e. are we playing God?)

Potential for Experimental abuse (doctors using patients as test subjects)

Germline treatment going from treating diseases to a method for picking the traits you want in a child (i.e. specifying hair and eye color)

Cutting DNA StrandsThe major tools of recombinant DNA technology are bacterial enzymes called restriction enzymes. Each enzyme recognizes a short, specific nucleotide sequence in DNA molecules, and cuts the backbones of the molecules at that sequence. The result is a set of double-stranded DNA fragments with single-stranded ends, called "sticky ends." Sticky ends are not really sticky; however, the bases on the sticky ends form base pairs with the complementary bases on other DNA molecules. Thus, the sticky ends of DNA fragments can be used to join DNA pieces originating from different sources.

                                                 

      

http://www.accessexcellence.org/RC/AB/WYW/wkbooks/SFTS/activity6.html

Creating Recombinant Plasmids

In order to be useful, the recombinant DNA molecules have to be made to replicate and function genetically within a cell. One method for doing this is to use plasmid DNA from bacteria. Small DNA fragments can be inserted into the plasmids, which are then introduced into bacterial cells. As the bacteria reproduce, so do the recombinant plasmids. The result is a bacterial colony in which the foreign gene has been cloned.

http://www.accessexcellence.org/RC/AB/WYW/wkbooks/SFTS/activity6.html