Lab - DNA Extraction

Olivia Williams
Lab #1
DNA Extraction
To extract DNA from a banana
Apparatus/Materials: salt, distilled water, liquid dishwashing detergent, ice-cold 95%
ethanol, banana, ziplock plastic bag, beaker
1. A ripe banana and distilled water was placed in the plastic bag, then sealed and mashed to
make it slurry.
2. Liquid detergent and salt was added to the bag. Then mixed for about a minute until the
detergent dissolves in the water.
3. Excess foam was then filtered off.
4. The liquid mixture was poured into a beaker.
5. Ice-cold ethanol was placed in a beaker.
6. Let the tube sit for 2-3 minutes without disturbing the solution.
7. Observations were then made.
After the addition of ethanol, a white slimy substance surface on top of the filtrate.
The banana DNA was easy to see as it was a white and it was chunky and had thick pieces
when picked up, but it appeared shredded in the liquid.
Deoxyribonucleic Acid, DNA, is a biological macromolecule that carries hereditary
information in many organisms. DNA is necessary for the production of proteins, the
regulation, metabolism, and reproduction of the cell. DNA is circular and lies free in the
cytoplasm of prokaryotic cells but are linear and contained in a nucleus of eukaryotic cells.
DNA is associated with proteins and RNA (ribonucleic acid) to form chromosomes.
Chromosomes are thread-like structures which contains nucleic acids. In this experiment,
DNA was extracted from a banana. DNA is found in the cells of every living organism. It is
incredibly small (90-600nm), but we can see it by extracting DNA and isolating chains of it.
A “filtrate” is made of bananas and treated with a buffer containing salt (NaCl) and distilled
water. The salt solution acts as a buffer to maintain a constant pH and binds up the positive
ions to prevent enzymes from destroying the DNA.
All cells are surrounded by the cell membranes, are composed of lipids, proteins, and
carbohydrates that are arranged in a “mosaic-like” manner. The soap solution contains
sodium laurel sulphate, which causes the cell membrane to break down by emulsifying the
lipids and proteins which allows the cell membrane to break apart. Once these membranes are
broken apart, the DNA is released from the cell. The salt enables the DNA strands to come
together, or aggregate due to the metal (sodium) ion shielding the negative phosphates of the
DNA which allows these ends to come closer so that they can precipitate out of a cold
alcohol solution.
The DNA clumps are soluble (can be dissolved) in some liquids, but not in alcohol. The DNA
precipitates out of the solution when the alcohol is added. The alcohol separates the DNA
from the other cell components, which are left behind in the water solution.
1. Ensure to add excess ethanol to the filtrate so that all DNA molecules can precipitate out
of the solution.
2. Ensure to keep reagents away from the body.
3. Ensure to use gloves.
It can be concluded that DNA can be extracted from a fruit by the use of a soap, salt and an
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