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Unit 2: Genetics
NTH 12: How can we isolate (pull out) DNA from an organism?
Outcome 6: Identify and describe DNA structure and explain its importance in genetics.
Introduction
In class we’ve been talking about how offspring inherit traits from their parents. We
know that they inherit alleles, which are copies of genes, by receiving DNA from their
parents. We also know that the DNA is located within a chromosome inside the
nucleus of a gamete, or sex cell.
We can actually look at an organism’s DNA by using a simple technique of isolating
(separating) the DNA from the rest of the cell. This is important when scientists
genetically modify organisms. Scientists first identify (say) which gene they want to
change, and then they isolate (separate) that from the rest of the cell so they can
change it.
Materials
1. 1 bottle of Cell Lysis Solution
2. 1 bottle of DNA Precipitation
Solution
3. 1 strawberry
4. 1 plastic tray
5. 1 test tube
6. 1 SEPUP funnel
7. 1 funnel with a long stem
8. 1 plastic sleeve
9. 1 plastic bag
10. 1 cheesecloth square
11. 1 wood splint
12. 1 graduated cup
13. 1 dropper
Procedure
1. Place the strawberry into the plastic bag and mash it with your fingers until there
are no lumps (chunks) of strawberry.
2. Place the SEPUP funnel over the first two cups of the plastic tray.
3. Place the funnel with the long stem in SLOT A of the funnel.
4. Place a piece of cheesecloth in the funnel that is in slot A.
5. Measure 10 mL of Cell Lysis Solution in a graduated cup and add it to the plastic
bag. Squeeze this mixture SLOWLY for 1 minute – try not to create any bubbles.
6. Slowly pour the mixture into the funnel with the cheesecloth. Let the solution drip
for approximately (about) 5 minutes. DO NOT allow any strawberry mixture to
fall into the plastic tray.
7. The liquid that collects in the cup is called the lysate, or the part of the cell that
was released. The lysate contains the DNA. Observe the lysate and record your
observations below.
Observations of lysate:
8. Place the plastic sleeve in one of the empty cups of the plastic tray.
9. Fill a test tube approximately half full with DNA Precipitation Solution. Place the
test tube in the cup supported by the plastic sleeve.
10. Use a dropper to pick up the liquid lysate.
11. Pick up the test tube and hold the tube at a 45-degree angle. Slowly drip the lysate
down the inside of the tube.
12. Let the tube sit for at least 3 minutes. Record you observations of the liquid in the
space below.
Observations of liquid:
13. The DNA will collect at the interface of the lysate and the DNA Precipitation
Solution. (The interface is where the two layers meet.) Place a wooden splint
into the test tube at the interface.
14. Gently turn the wooden splint so the DNA wraps around the end of the splint.
15. Examine the isolated DNA and record your observations on the next page.
Observations of isolated DNA: