Biology 1B Lab Report for DNA Banana Extraction Lab
Name:
Background: DNA is found in the cells of every living organism. Each organism
has its own specific genetic code or blueprint. In this lab investigation we will
extract DNA from a banana and by isolating chains of it you will be able to gain
some knowledge and understanding. (B4.2C, B4.2B and Scientific Logic and
Reasoning)
The soap solution contains sodium laurel sulfate, which can break up fats and
proteins. During the DNA extraction, the soap pulls apart the fats (lipids) and
proteins that make up the membranes are broken apart, the DNA is released
from the cell. The salt enables the DNA strands to come together. When alcohol
is added to the solution it separates the DNA from the other cell components,
which are left behind in the water solution.
Title: ______________________________________________
Purpose of the lab:
_________________________________________________________________
Materials: section of banana (can also use strawberries), distilled water, plastic
sealable bag, plastic cup or beaker, shampoo, table salt, chilled isopropyl alcohol,
spoon, coffee filter, clear narrow tube or jar, (optional- bamboo skewer and
capped tube)
Safety: 1. __________________________________________
2. __________________________________________
Pre-lab questions:
1. What is the goal of this lab?
___________________________________________________________
2. How does this lab relate back to the DNA unit?
___________________________________________________________
3. Why do we use soap in this lab?
___________________________________________________________
4. What is one of our safety concerns?
___________________________________________________________
Procedure:
1. Get your section of banana, remove peel and discard. Put banana in
plastic bag, with 60 MLS of distilled water. Mash to make slurry.
2. In the plastic cup, mix a solution of 1tsp. of shampoo/dish soap, 2 pinches
of salt and 20 MLS of distilled water. Stir this solution slowly for about a
minute until soap dissolves in water.
Diagram cup,
filter secured
with rubber
band:
3. Now you will add 2 tsp. of the banana slurry to the soap solution and stir
for 5 minutes.
4. Next, make a well with the coffee filter and place it in a empty clean cup.
Do not let the filter touch the bottom of the cup (you could secure the
filter on the rim of the cup with a rubber band) Pour in your liquid mixture
slowly and allow to filter.
5. Fill the narrow tube with 5 MLS of cold isopropyl alcohol. Very slowly, add
some of your filtered banana slush mix into tube.
6. Let the tube sit for 2-3 minutes without disturbing the solution. You will
see the clear/white DNA precipitate into the alcohol layer.
What’s going on? DNA (deoxyribose nucleic acid) is found in the cells
(specifically the nucleus) of every living organism. It is incredibly small, but we
can see it by extracting DNA and isolating chains of it.
The soap solution contains sodium laurel sulfate, which can break up fats and
proteins. During the DNA extraction, the soap pulls apart the fats (lipids) and
proteins that make up the membranes are broken apart, the DNA is released
from the cell. The salt enables the DNA strands to come together. When alcohol
is added to the solution it separates the DNA from the other cell components,
which are left behind in the water solution.
Results: Record your observations below. Describe the appearance of the DNA.
Conclusion: POST LAB DISCUSSION:
1. Where do you find DNA in the cell?
2. Why did we add soap to the banana/strawberry?
3. Why did we add salt to the banana/strawberry?
4. Explain what happened in the final step when you added ethanol to your
banana/ strawberry extract. (Hint: DNA is soluble in water, but not in
ethanol)