Lab : DNA Strawberry Extraction
Hypothesis
Strawberries have DNA that has the ability to be extracted and also to be seen under a microscope.
Explanation of Hypothesis
All livings things have some sort of genetic code. Strawberries are not an exception to this rule, and in strawberries this genetic code is called DNA. The DNA has the ability to be extracted due to it having a different molecular nature than the rest of the cell.
Variables
Dependent
The amount of DNA extracted from the strawberry
Independent
The size of the strawberries
Fixed
Time of which ethanol and strawberries are left together
Temperature of ice in which the ethanol is held
Amount of extraction buffer used
Amount of ethanol used
Type of strawberries used
Type of microscope used
Time of which strawberries are smashed for
Time of which extraction buffer and strawberries are mixed together
Strainer used
Uncontrolled
Microscope visibility
Room temperature
External light
Observation
Watch carefully and record what you observe where the ethanol meets the filtrate layer.
The solution separates into two layers, with the red filtrate at the bottom, the white ethanol on top, with some air bubble like mixture of both in the middle.
Let the solution sit for two minutes without disturbing it. Describe the precipitate.
A clump of pinkish air bubbly DNA with countless tiny bubbles form from the filtrate at the bottom. Gradually, it rises up through the clear ethanol layer, becoming more white and clumped into a ball. Until it floats to the top, where it condenses and weaves together.
View and describe the DNA with the naked eye and under the microscope.
The DNA is pinkish white, sticky, and wet-cotton-like mass under naked eye.
Microscope Diagram is attached.
Discussion
1) What is the purpose of mashing the fruit?
It is a mechanical disruption of cells that helps to break down the cell walls.
2) What is the purpose for the shampoo and salt in the DNA extraction buffer?
The detergent in the shampoo dissolves the phospholipids bi-layers of the cell and organelle membranes. The positive charged sodium ions in the extraction solution are attracted to the negatively charged phosphate groups on the DNA backbone. It neutralizes the DNA’s electric charge. The salt also keeps the proteins in the extract layer so they aren’t precipitated with the DNA.
3) What is the purpose of the ethanol?
The cold ethanol is used to separate the DNA from the strawberry protein. DNA is soluble in water, but not in ethanol. Therefore the DNA can be separated from the solution.
4) Relate the chemical structure of DNA to how it looks when clumped together.
At a molecular level, the chemical structure of DNA is a double twisted helix. Normally, it cannot be seen with the naked eye. It can only be seen when the cell is n prophase of mitosis, meaning that the DNA has folded itself to form chromatin. When the strawberry DNA is clumped together, our naked eye sees a white mass, but when looking at it with a microscope; we can see that the clumped mass is composed of interlocking strands that are “woven” together.
5) Would you expect scientist to use the exact same method to extract DNA from human tissue? Why or why not?
Yes, I would expect scientists to use the exact same method to extract DNA from human tissue because the procedures done in this lab use the same essential elements as advanced laboratory DNA extraction procedures, such as, mechanical disruption of cells, liberation of the DNA, and precipitation of the DNA.
6) Which human cells would you use for DNA extraction and why?
The most common human cells that would be used for DNA extraction are hair, skin and saliva because there is an abundant source of them and it is painless and easy to obtain it. Blood is also easy to obtain, but a bit of pain can be side effect.
7) Why do you think scientists study the DNA of strawberries?
Scientists use the study of DNA because strawberries have enormous genomes, they are octoploid (8 copies of each gene). They also produce pectinases and cellulases which start the breakdown of cell walls as they ripen.
8) Is the DNA pure? What other molecule normally associated with DNA will be present?
No, DNA is not pure. It also has protein molecules embedded within it. For example, there are strawberry proteins because it is slightly pink.
9) Some people are concerned that manipulation of DNA will change life as we know it. Provide two examples of human genes that might be modified.
Human genes have been modified to provide resistance to illnesses and diseases, especially genetic diseases. Also, some human genes may be manipulated to change things such as lung capacity, brain capacity and muscle mass to make a “super” human.
10) Provide two examples of plant genes that already modified and the reasons for the modification.
Bananas – Some are modified to produce human vaccines against infectious diseases such as hepatitis B.
Fruit and nut trees yield years earlier and plants that produce new plastics with unique properties.
Conclusion
DNA can be found in all living organisms such as humans, animals, plants and fruits. For this lab, a strawberry was used to help identify the molecular structure of DNA and to demonstrate how DNA is extracted from any organism. The molecular structure of DNA is a double twisted helix made up of two complementary strands. This, at a molecular level, cannot be seen with the naked eye. It can only be seen when the cell is in prophase of mitosis, meaning that the DNA has folded itself to form chromatin.
The strawberry DNA that was extracted could be seen with the naked eye because it was an extractable clumped mass of thousands of strands of DNA. Looking at the small chunk closely under a microscope, the clump mass is actually composed of interlocking woven strands of DNA. While looking at the DNA through the microscope, it is also visible that there are proteins embedded within it. The procedures to extract DNA from a strawberry are relatively similar to advanced laboratory DNA extraction procedures.
Both require a mechanical disruption of cells, liberation of the DNA, and precipitation of the DNA. With the strawberries, molecules were mashed in order to break the cell wall, then, they were chemically added the DNA extraction buffer made from shampoo and salt, and used ethanol to separate the DNA from the solution. The salt in the buffer neutralizes the negatively charged phosphate groups in the DNA. The ethanol separates the DNA from the strawberry protein because DNA is soluble in water but not soluble in ethanol. Having enormous genomes, strawberries were an ideal specimen to use to identify DNA.
Evaluations
Throughout the whole lab, one can find possible errors (weaknesses and limitations)
– Did not specify a specific temperature for the cold ethanol. May cause erroneous outcomes in the separation of DNA and the solution.
– Getting the DNA off the inoculating loop was problematic. It is possible that the DNA was mashed and affected during this procedure of applying the DNA onto a slide. Hand was needed.
– May cause erroneous results in the efficiency of the buffer due to a specific type of shampoo for the mixing of the DNA extraction buffer.
– No specific safety rules or conduct was implied or listed. May cause danger or injury to experimenters.
In order to improve this DNA Strawberry Extraction for further usage, the following improvements can be made in respect to the weaknesses and limitations found above.
– Provide and state another way of getting the DNA off the inoculating loop. Possibly, the use of another inoculating loop, the use of toothpicks, or even the use of hands.
– Specify, in the procedures or materials, a specific temperature for the cold ethanol and one should be able to maintain that temperature..
– Specify, in the materials, a specific type of shampoo and strawberry for the mixing of the DNA extraction buffer.
– List or state some safety rules or conduct regarding the lab. Even small safety details never hurts.
