SC5L1
Aim:
DNA Extraction
To investigate the structure of DNA extracted from the cells of split
peas.
Hypothesis: It is predicted that the insides of the nuclei of the split peas will contain
a swirl like form of DNA.
Materials:


















½ Cup dried split peas.
Vitamiser or blender
Large beaker
Dishwashing detergent
Meat tenderiser
Test-tube rack
Dropping pipette
Methylene Blue
Light microscope
200ml water
Fine mesh kitchen strainer
Glass rod
Spatula
Large test-tube
Small beaker of alcohol
Microscope slide and cover slip
Paper towelling
Microscope lamp
Method (Part A):
1. Place the peas and water in the blender and process for
about 20 minutes.
2. Pour the mixture through the kitchen strainer into a large
beaker
3. Add about 80ml of dishwashing detergent to the strained
mixture and stir thoroughly using a glass rod
4. Add a generous spatula of meat tenderiser to the mixture
and continue stirring, though not too vigorously, for about 5
minutes.
5. Quarter-fill a large test-tube with the pea mixture
6. Gently pour about the same quantity of alcohol down the
side of the test tube. The alcohol should form a layer on top
of the mixture.
7. Observe the mixture for a few minutes. A white, thread like
substance should rise from the pea mixture and float above
the alcohol layer. This is the DNA of the split peas.
Darren Lay
SC5L1
DNA Extraction
Method (Part B):
1. Use a dropping pipette to carefully remove some of the
tread-like substance from the top of your test-tube
preparation.
2. Place one ore two drops onto the middle of a microscope
slide.
3. Add two drops of the Methylene blue. Wait 3 or 4 minutes
to allow the Methylene blue to be absorbed by the DNA.
4. Carefully place a cover slip on the slide. Gently press a
folded piece of paper towelling over the top of the prepared
slide to soak up any excess liquid.
5. Observe the DNA first under low power, then high power.
Results:
This image is a representation of what could be seen
under the 40x magnification. This is not a very
detailed and close up image, only showing patches
with white dots.
This image is a representation of what could be seen
under the 40x magnification. A long string like
substance can be seen on the bottom right.
Darren Lay
SC5L1
DNA Extraction
Discussion:
When the alcohol was added into the pea mixture, the DNA was separated from the
mixture and a white thread like substance rose to the top of the test tube. The DNA
was then extracted and placed between glass slides where it was then examined under
the microscope. The results show that when the DNA was looked at under the
microscope, white thread like swirls could be seen. The hypothesis was supported as
only a swirl like form of DNA could be seen even through the highest power
magnification. The structural features of the DNA could not be seen and the double
helix figure was not observed.
In this experiment, an error occurred when putting the glass slides together. Air
bubbles formed and the DNA became hard to distinguish. This had an impact on the
results as a portion of the observed DNA could in fact have been air bubbles.
An inadequate amount of sampled DNA could also have been an aspect of the DNA
being hard to distinguish. When the slides were observed under the microscope, large
white spots could be seen but the DNA could not be seen until the slides were moved
around.
This experiment could have been improved by carefully putting the glass slides
together in order to prevent air bubbles from forming, and by extracting a larger
sample of DNA to observe. It could also have been improved by taking more samples
and doing more observations. This could have a major impact on the accuracy of the
results.
Darren Lay