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Extraction of DNA from a Banana
ABSTRACT
- Every cell’s nucleus contains “instructions” for growth and functioning, housed in deoxyribonucleic acid (DNA).
- DNA encodes a detailed set of plans, or blueprints, used by living organisms.
- DNA is found in almost all living organisms, including bananas and humans, and is passed from generation to generation.
- Genes, which make up DNA, direct the body’s development, functioning, and unique traits (e.g., hair and eye color).
- This experiment extracts DNA from a banana using common household materials, making the typically invisible molecule observable.
AIM
- To extract DNA (Deoxyribonucleic Acid) from fruits such as bananas and strawberries.
INTRODUCTION
- Deoxyribonucleic acid (DNA) is a molecule that holds the genetic instructions for growth, development, and reproduction in all living organisms and many viruses.
- DNA and ribonucleic acid (RNA) are nucleic acids, one of four key macromolecules in life alongside proteins, lipids, and carbohydrates.
- DNA consists of two strands coiled into a double helix. These strands are made up of nucleotides, each containing:
- Nitrogenous bases: cytosine (C), guanine (G), adenine (A), thymine (T).
- Sugar: deoxyribose.
- Phosphate group.
- The nitrogenous bases are paired (A with T, C with G) and held by hydrogen bonds. This structure stores biological information and is resistant to cleavage.
- DNA replication allows for the transmission of genetic information during cell division.
- Eukaryotes (plants, animals, fungi) store DNA in the nucleus and organelles like mitochondria. Prokaryotes (bacteria) store DNA in the cytoplasm.
- History: DNA was first isolated in 1869 by Friedrich Miescher. Its structure was identified by James Watson and Francis Crick in 1953, aided by Rosalind Franklin’s X-ray diffraction data.
MATERIALS REQUIRED
- ½ peeled ripe banana (other fruits like strawberries may also be used).
- ½ cup hot water.
- 1 tsp salt.
- ½ tsp liquid dishwashing soap.
- Resealable zip-top bag (quart size).
- Cold rubbing alcohol (isopropyl alcohol), stored in the freezer.
- Coffee filter.
- Narrow glass.
- Wooden stirrer.
PROCEDURE
- Prepare the banana mixture:
- Mash ½ peeled banana in a resealable bag or container with ½ cup of hot water.
- Prepare soap solution:
- Mix 1 tsp of dishwashing soap with ¼ tsp salt in a cup.
- Add 2 tbsp of water and stir gently to avoid foam.
- Combine solutions:
- Add 2 tbsp of the banana mixture to the soap solution. Stir for 10 minutes.
- Filter the mixture:
- Place a coffee filter into a clean container, ensuring it doesn’t touch the bottom.
- Pour the banana-soap mixture into the filter. Allow the filtrate to collect at the bottom for about 10 minutes.
- Add alcohol:
- Slowly add rubbing alcohol to the filtrate, creating equal parts filtrate and alcohol.
- DNA will appear as a white layer between the two liquids.
- Extract DNA:
- Let the mixture sit for 10 minutes.
- Use a wooden stirrer to gently spool the visible white DNA from the alcohol layer.
OBSERVATION & ANALYSIS
- Saltwater: Prepares the DNA to stick together in clumps, making it visible.
- Dish soap: Breaks down the cell and nuclear membranes, releasing DNA.
- Alcohol: DNA is insoluble in alcohol, causing it to clump and form visible strands.
CONCLUSION
- The extracted DNA will appear white and form string-like strands. This extracted DNA can be collected using a wooden stirrer.
