Gene Technology Chapter 9

“I Can” Statements I can explain how restriction enzymes can be used to make recombinant DNA. I can explain how bacteria can be used to produce products such as human insulin. I can describe the process of gel electrophoresis. I can examine DNA banding patterns to make conclusions about crime scenes and paternity. I can give examples of how gene technology is used in agriculture and in raising animals. I can explain the difference between reproductive cloning and therapeutic cloning.

Genetic Engineering Purpose: using genes for practical purposes like… –Producing human insulin in the lab Used to have to use cow/pig insulin Not as good as human insulin –Inserting a gene into a tomato to give it better flavor In the following slides, we will describe how we can “trick” bacteria into producing human insulin

Restriction Enzymes Enzymes that look for specific sequences in DNA and then cut DNA at that location Example of a restriction site: –GAATTC Restriction enzymes come from bacteria –Natural use: Bacteria use them to protect themselves from viral attack –Lab use: Create recombinant DNA

Steps in Genetic Engineering (Insulin Example – see diagram on p.261) Step 1: Cut DNA –Use a restriction enzyme to cut the gene of interest – in this example, the insulin gene is cut out of human DNA –Use the same restriction enzyme to cut open a plasmid (a circular piece of DNA) Step 2: Make recombinant DNA: contains DNA from TWO sources –Insert the gene of interest (insulin gene) into the plasmid –Use ligase (another enzyme) to hook them together

Step 3 – Cloning the gene –Insert the plasmid (now containing the gene of interest for insulin) back into the bacterium –Each time the bacterium reproduces, the plasmid and the gene of interest are copied Step 4 – Screening and Product Production –Screening: Pick out the bacterial cells that contain the plasmid and are able to make insulin –Use the bacteria to produce human insulin!

Steps in Genetic Engineering

Gel Electrophoresis Purpose – a way to separate pieces (fragments) of DNA based on size How it works: Step 1: Cut DNA up into pieces Step 2: Load the DNA into a gel (see the picture on the following slide) Step 3: Turn on the electricity! –DNA is negatively charged –It will migrate (travel) toward the positive charge –The smaller pieces of DNA will travel through the gel faster and will end up further away from the wells Step 4: Analyze the banding pattern!

Gel Electrophoresis

Gel electrophoresis is used for many things, including DNA Fingerprinting No two people have the same DNA If you use the same restriction enzyme to cut DNA from person A and DNA from person B, you will get two different sets of DNA fragments (different lengths and numbers of fragments) Use gel electrophoresis to separate the fragments  person A and person B will have different banding patterns on the gel Use this for… –Crime scene analysis –Paternity testing

Crime Scene Analysis S1 – suspect 1 S2 – suspect 2 E – evidence (blood) from the crime scene Who is guilty???

Paternity Testing – Example #1 Who’s the father???

Paternity Testing – Example #2 Case #1 - Is he the father? Case #2 - Is he the father?

Genetic Engineering: Agriculture Can be used for… Improving crops (insert gene into organism) –More tolerant to drought conditions –Soybeans that are resistant to weedkillers (easier to kill weeds without also killing the crop) –Tomatoes that ripen without becoming soft –Increase levels of iron in rice There are risks: –Weeds may become resistant to weedkillers –Important to consider food allergies

Genetic Engineering: Animals Can be used for… Increasing milk production (cows) by adding growth hormone to diet Making products that are medically useful –Add a human gene to the cow –The cow will produce the human protein (like human growth hormone) in their milk Cloning – two types that are very different! –Therapeutic –Reproductive –See following slides

Reproductive Cloning Purpose: Make another individual that is genetically identical to the donor Example: Dolly the sheep was the first cloned mammal (1997). She is genetically identical to the adult sheep that donated the genetic material needed to make Dolly. Therapeutic Cloning Purpose: Make tissues or organs that are genetically identical to the donor Example: Sue has liver disease and needs a new liver. Using therapeutic cloning, a new liver could be produced and transplanted into Sue’s body.