New seats! Please stand along the perimeter.

Science Log: DNA Extraction Lab Preview- pg. 30 Define extraction in your own words. Why might scientists want to extract DNA? What are your predictions for how DNA will look?

DNA Extraction - Steps Collect cells Burst cell membranes open - salt Dissolve lipid (fat) layer - soap Separate DNA from proteins and debris - salt Isolate concentrated DNA – 91% Isopropyl Alcohol (stored in freezer)

Measure 10 ml of water

Take the green part off the strawberry

Add the strawberry, 10 ml. water, and 3 pinches of salt to the baggy.

“Smoosh” the strawberry with your fingers

Use the stick to get 4 drops of soap

Add 4 drops of soap to the baggy

Gently rock the baggy back-and-forth (so you don’t make bubbles)

Put the coffee filter into the funnel

Slowly pour the strawberry juice into the filter

It takes time to filter through Slide 11

Add only a pinch of meat tenderizer (enzyme) and pour the juice into the smaller beaker or test tube Slide 12

Slide 13

Tilt both containers when you pour the alcohol down the side Slide 14

Pull the DNA out with the pipette

The science behind the fun Did you know that DNA is in the food you eat? The long thick fibers you pull out of the extraction solution are strands of strawberry DNA. DNA is present in every cell of all plants and animals and determines the genetics of the individual organisms.   While other fruits are soft and just as easy to pulverize, strawberries are the perfect choice for a DNA extraction lab for two reasons: they yield more DNA than any other fruits, and they are octoploid, meaning that they have eight copies of each type of DNA chromosome. These special circumstances make strawberry DNA easy to extract and see. (Human cells are generally diploid, with only two sets of chromosomes.)

THE SCIENCE BEHIND THE FUN To extract the DNA, each component of the extraction solution plays a part. The soap helps to dissolve the cell membranes. The salt is added to break up protein chains that hold nucleic acids together, releasing the DNA strands. Finally, DNA is not soluble in isopropyl alcohol, and even less so when the alcohol is ice cold.

Drawing Conclusions – separate sheet of paper 1. Why was it necessary to add salt to the mixture? 2. Why was it necessary to add soap to the mixture? 3. What did the DNA look like? 4. Explain how DNA is stored in the nucleus. 5. Explain what happened in the final step when you added the alcohol. 6. List two reasons why it is important for scientists to remove DNA from an organism.