DNA IN OUR FOOD? EXTRACTION OF DNA FROM STRAWBERRIES (GETTING THE DNA OUT OF STRAWBERRIES) -OR ANYTHING ELSE-
QUESTIONS TO PONDER • WHAT IS DNA? • WHERE IS IT FOUND? • CAN YOU SEE DNA? • WHAT DOES IT LOOK LIKE?
WATCH THIS! https://www.youtube.com/watch?v=J3Pf1XKrn-Q
I NOTICE… AS A GROUP , FINISH THE SENTENCE… WRITE THIS DOWN ON AN INDEX CARD/POST-IT NOTE
I WONDER… AS A GROUP , FINISH THE SENTENCE… WRITE THIS DOWN ON AN INDEX CARD/POST-IT
HOW DO YOU GET THE DNA OUT OF THE STRAWBERRY?
PLANT CELL
GETTING THE DNA OUT! 5 steps: 1. Make the extraction buffer. 2. Squishing the strawberries (Manual tissue disruption) 3. Breaking open cells (Lyse cells) 4. Making sure the DNA does not have a charge (Neutralization of DNA polarity) 4. Getting the DNA out using alcohol (DNA extraction)
Step 1: Make the extraction buffer Extraction buffer consists of: detergent, salt and water. Extraction Buffer + + =
Step 2: Getting the DNA out! 2. Squishing the strawberries (Manual tissue disruption) • Squish the strawberries with physical force (hands) • Massage gently
Step 3. Breaking open the cells (Lyse cells) a) Break open the cells with a extraction buffer containing soap or detergent to destroy the fats and lipids that make up the cell membrane Soaps work via polar interactions
3. Making sure DNA does not have a charge (neutral) • Add salt (NaCl) to neutralize the negative charges on DNA
3. Making sure DNA does not have a charge(neutral) The role of electric charge and polarity • Water is polar which means that it has both a positive and a negative side. • It forms a “hydration shell” around ions. • This is what it means to be soluble (does salt disappear when you put it in water and stir? This means it is soluble.) • In order for a molecule to be soluble in water, it needs to be a polar molecule or have a charge (negative or positive.) Water DNA -
Why do we add more salt (NaCl) Na + ions: They out-compete the water molecules Positive and negative charges cancel each other out. DNA is now neutral. - - - DNA - - - The positively charged sodium ions neutralize the negative charge on the DNA, making it less hydrophilic � less soluble in water. This is how we separate DNA from all the other cellular components
4. Getting the DNA out using alcohol (DNA Extraction) • DNA is separated from the lysis buffer by the addition of an alcohol (isopropanol). • This causes the DNA to “fall out” or precipitate out of the solution. • There’s so much DNA that you can see it and get it on a stirring rod!
Which is more polar (has more charge)? + Polar region - Non-polar region Our DNA its surrounded by NaCl or salt and is nonpolar (hydrophobic). It prefers to be in an alcohol solution rather than water. + + - Water (H 2 O)
THE FUN BEGINS! THE LAB!
FIRST, SOME WORDS TO KNOW Cheesecloth Funnel
MORE WORDS TO KNOW Small beakers Test Tube
WORDS TO KNOW Stirring Rod Inoculation Loop
WORDS TO KNOW Spooling Interface
WORDS TO KNOW Extraction Buffer DNA
WHAT YOU WILL NEED
STEP 1 GET READY - MAKE EXTRACTION BUFFER
STEP 2
STEP 3 Squeeze, massage and squish gently, mixing for 1 minute.
STEP 4
STEP 5 Squeeze, massage and squish gently, mixing for 1 minute.
STEPS 6 AND 7
STEP 8
STEP 9
STEP 10
QUESTIONS? • WHAT WERE THE QUESTIONS WE POSED AT THE BEGINNING OF THIS LAB? • DID WE ANSWER THEM? • MORE QUESTIONS? � IT’S OK TO HAVE MORE QUESTIONS, THAT’S WHAT SCIENCE IS ALL ABOUT!
QUESTION FOR YOU! NOW THAT YOU HAVE DNA WHAT IS IT USED FOR?
LOOK AT IT UNDER A MICROSCOPE Banana DNA stained with toluidine Image from: http://www.funsci.com/fun3_en/dna/dnaen.htm
USE PCR TO MAKE LOTS OF COPIES OF A STRING OF SEQUENCES OF DNA Image from: http://www.openwetware.org/wiki/CH391L/S12/PCR_and_advanced_PCR_techniques
SEQUENCE THE DNA Image from: https://en.wikipedia.org/wiki/Genome Image from:https://en.wikipedia.org/wiki/DNA_sequencing
USE IT FOR FORENSICS OR DNA FINGERPRINTING Image from : http://legacy.hopkinsville.kctcs.edu/instructors/Jason- Arnold/VLI/Module%201/m1DNAfunction/m1DNAfunction_print.html
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