Download Investigation of the structure of DNA

Investigation of the structure of DNA
Aim: To extract DNA from Split Peas and observe the structure of the DNA.
Hypothesis: The observation of DNA extracted from Split Peas is predicted to be a
tessellation of nucleotides, making strands of double helix structures, therefore strands
are expected to be observed. However it is not expected to see the three main groups
of a nucleotide (sugar, phosphate and base).
Materials:
½ cup of dried split peas (soaked overnight)
large beaker
Meat tenderiser
dropping pipette
Light microscope
Fine mesh kitchen strainer
Spatula
Small beaker of alcohol
Paper towelling
Vitamiser or blender
Dishwasher detergent
Test-tube rack
Methylene blue
200mL of water
Glass rod
Large test-tube
Microscope slide and cover slip
Microscope lamp
Method:
Method 1: Place the peas and water in the blender and process for about 20 seconds
or until the mixture is of thin, soupy consistency.
Method 2: Pour the mixture through the kitchen strainer into a large beaker.
Method 3: Add about 80mL of dishwashing detergent to the strained mixture and stir
thoroughly using a glass rod.
Method 4: Add a generous spatula of meat tenderiser to the mixture and continue
stirring, though not too vigorously, for about 5 minutes
Method 5: Quarter-fill a large test-tube with the pea mixture.
Method 6: Gently pour about the same quantity of alcohol down the side of the testtube. Tilting the test-tube will make this easier to do. The alcohol should form a layer
on the top of the pea mixture.
Method 7: Observe the mixture for a few minutes. You will see a white, thread-like
substance rise from the pea mixture to rest above the alcohol layer. This is the DNA
that you have extracted from the cells of the peas.
Method 8: Use a dropping pipette to carefully remove some of the thread-like
substance from the top of your test-tube preparation.
Method 9: Place one or two drops onto the middle of a microscope slide.
Method 10: Add two drops of Methylene blue. Wait 3 or 4 minutes to allow the
Methylene blue to be absorbed by the DNA
Method 11: Carefully place a cover slip on the slide. Gently press a folder piece of
paper towelling over the top of the prepared slide to soak up any excess liquid.
Method 12: Observe the DNA in three different slide powers, 4x, 10x and 40x
Results:
Slide Power
Description
4x
Blue (from Methylene
Blue) ribbon-like strands
lapping over each other,
small but visible bubbles
were observed on the
strands of DNA.
10x
The DNA strands were
curled in some areas.
Larger bubbles than 4x
surrounding ribbon-like
DNA.
40x
Picture
Straight close-up strands
of string/thin strands of
DNA, textured like
ribbons.
Results showed that power 40x is more textured and detailed than the other powers.
However the power 4x showed more variety of sizes and shapes of substances,
strands, bubble and shadings of different colours. (blue and green)
Discussion:
This experiment was successful. It clearly indicates that there were strands, assuming
they were built up by tesselations of double helix structures; however this experiment
was not able to prove that double helix structures were observed. In discussion there
were still material-like strands observed after DNA was extracted from split peas. The
prediction to view strands of double helix structures was supported.
Minutes after the alcohol was poured in with the pea mixture, visible small and big
white cotton-like substances began to form, DNA. The DNA under the microscope in
low slide power was material-like in description, high slide power, and observations
showed a close-up view of only a few strands of DNA.
Methylene blue was used into the DNA before put under the microscope to make it
easier to observe. Inaccurate timing of letting the DNA absorb the methylene blue
may have an impact of description when put under the microscope.
Attempt one of putting the DNA under the microscope, small bubbles of methylene
blue was floating around and moving freely, due to the short amount of time of wait
when DNA was absorbing methylene blue. Uncontrolled variables such as the exact
quantity of DNA was extracted to observe, the focus of the microscope used, this
experiment could've been improved if a photo of the observations were taken instead
of sketching; it is more accurate and precise.
Conclusion:
Overall this experiment clearly indicates that the DNA extracted from the split peas
showed material-like textured strands/strings when observed under the microscope.
The aim and hypothesis for this experiment was somewhat supported by the results.
Strands (assumed to be composed out of millions and thousands of joined double
helix structures, however it is not proved) were observed as expected. One drop of
Methylene Blue was applied onto the DNA to assist the naked eye to observe.
By Misha Lay