Biological Science and Extraction of DNA from Kiwi Fruit - Assignment Example

Extraction of DNA from Kiwi fruit Extraction of DNA from a Kiwi (Actinidia deliciosa) fruit was attempted using simple household items. The fruit was peeled, chopped and macerated with extraction buffer made from washing up liquid, salt and water. The mixture was incubated at 600C for 15 minutes using a home-made water bath and the mixture was then filtered with a coffee sieve. Finally, DNA was separated by adding ice-cold methylated spirit and was observed as white substances at the junction of alcohol and Kiwi fruit mixture. This proved to be a successful method to extract DNA from a Kiwi fruit in a quantity that permit visualization without a high-power microscope. INTRODUCTION DNA (deoxyribonucleic acid) is the basic structure of all living organisms (plants, animals, humans, microbes) and is present in the cells, especially in the cell nucleus. They are made from simple units known as ‘nucleotides’. Genes, which carry all information (structure, behavior, functions) of a cell or an organism, are made from long strands of DNA and this DNA is copied and inherited through generations from parent to the offspring. Hence, DNA is used in producing genetically modified plants and animals, in identifying variations/similarities of plant types, in medical research and in forensic medicine and in manufacturing pharmaceuticals (Jie, 2011). Isolated DNA from a tissue of a plant, animal, microbe or a human is therefore very useful since it provide much information about the individual, its characters and genetic background. There are many protocols of DNA extraction from an organism. Advanced techniques are needed to isolate DNA in a more pure form and require sophisticated equipment and specific chemicals. However, all these methods are based on three basic steps; i.e. separation and opening of cells chemically or mechanically to release DNA, purify DNA by removing proteins and other cell debris and finally, precipitation of DNA using an alcohol (Hoyle, 2011). If these basic steps are practiced, it should be possible to isolate DNA by following simple means and hence the objective of this study was to extract DNA from a Kiwi fruit using household items. MATERIALS AND METHODS A fruit of Kiwi (Actinidia deliciosa), otherwise known as ‘Chinese gooseberry’, was used to extract DNA. Outer skin of the fruit was peeled off and the fruit was chopped into small pieces using a knife. These pieces were put into a jar and mashed thoroughly to break open cells and enhance release of DNA. The Extraction buffer (Table 1) was added into fruit pulp and continued further mashing to enhance release of more DNA. Table 1. Composition of the extraction buffer Component Quantity Washing up liquid 5g Salt 2g Tap water 100ml All components were mixed and stirred slowly until salt was completely dissolved. This Kiwi - buffer mixture was then incubated at 600 C for 15 min. by carefully immersing the jar in a water bath. The water bath was prepared by filling a large basin with approximately equal volumes of normal tap water and boiling water from a kettle. The precise temperature was maintained by using a thermometer. After 15 minutes, the jar was removed from the water bath and the content was filtered through a fine sieve (coffee filter) into a fresh jar to separate Kiwi DNA from other cellular debris. Ice-cold alcohol was pre-prepared by freezing methylated spirit for a minimum of 30 min period and this was carefully poured down the inside of the jar containing Kiwi DNA suspension. RESULTS A yellow-green colored filtrate was observed after filtering the incubated mixture of fruit pulp and buffer. When ice-cold alcohol was added into this filtrate, a transparent layer was formed on top of the Kiwi mixture as alcohol has lesser density than the mixture. Gradually, a white substance began to appear at the bottom of the ice cold alcohol layer where it met the Kiwi DNA suspension. This white substance was Kiwi DNA and could be collected using a small spatula made from a curved paper clip. DISCUSSION Since all living things are made up of cells and each cell contain a complete set of the organism’s DNA, DNA can be extracted from any part of an organism. Plant cells are surrounded by a cell wall and inside the cell wall, a cell membrane (plasma membrane) covers the cell contents (nucleus, cytoplasm etc). Nuclei, which contains DNA is embedded in the cytoplasm (Figure 1). Thus, in order to release DNA from cells of the Kiwi fruit, all these cellular coverings have to be diffused. Mashing the fruit with extraction buffer help to break cells apart and expose cellular membranes. Protease enzymes in Kiwi fruit will breakup proteins in the cells and detergent in the washing up liquid dissolves fatty cell membrane by chemically reacting with the lipid layers around the cells and allow the cellular contents to be diffused into the suspension. When cellular contents are thus diffused, salt in the buffer makes DNA to combine together and separate from cellular debris during filter. High temperature (600C) during incubation further breaks down cell walls exposing cell membranes. DNA is insoluble in alcohol and when ice cold alcohol is mixed, it coagulates to form a white jelly-like substance that can be visually detected and collected (Figure 2). Cool temperature of alcohol will slowdown enzyme activity and prevent DNA breakdown. Kiwi is a good source of DNA as it has 6 copies of each type of chromosomes (Crowhurst, Whittaker and Gardner, 1992). This mass quantity will make it possible to visualize DNA with the naked eye. Results of this experiment showed that crude DNA from a Kiwi fruit could be extracted using simple household items. These DNA can be further purified through molecular biological techniques. CITED REFERENCES Carboni, G (2007). How to extract DNA from fruits. [Online] [Accessed 02 April 2011] Crowhurst, R N, D Whittaker and R C Gardner (1992). The genetic origin of kiwi fruit. Acta Hort (ISHS) 297:61-62 [On line] [Accessed 30 March 2011] Hoyle, M G (2011). Steps in DNA extraction [Online] < http://www.ehow.co.uk/how-does_5194458_steps-dna-extraction.html> [Accessed 01 April 2011] Jie, M W (2011).Uses of DNA extraction. [Online] [Accessed 30 March 2011] Kroening, M and D Trinklein (2007). MG2 Plants and their environment [Online] < http://extension.missouri.edu/publications/DisplayPub.aspx?P=mg2> [Accessed 01 April 2011] BIBLIOGRAPHY Schultz, T (2010). Easy life science lab activity: how to extract DNA from strawberries.[Online]. . [Accessed 02 April 2011] Read More