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    Isolation And Characterization Of DNA From Onion Biology Essay

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    The experiment was about the isolation and word picture of DNA. The Deoxyribonucleic acid was isolated from the onion. The mass of the stray DNA was 15.11 g. The pureness of stray DNA was estimated by ciphering the ratio based from the optical density at 260nm and 280nm resulted to 0.671 intending more protein was absorbed. Meanwhile in denaturation of DNA, the initial optical density at 260 nanometer was 1.304 higher than the optical density at 260 nanometers after heating which was 1.095.


    Deoxyribonucleic acid ( DNA ) is the familial stuff in worlds and all other beings. DNA isolation is the remotion of Deoxyribonucleic acid from the cell which it usually resides. Isolation is the remotion of Deoxyribonucleic acid from the cell in which it usually inhabits. ( 1 )

    Onions are used since it contains small sum of amylum which allows the Deoxyribonucleic acid to be more seeable. The filtrate is made up of onions treated with salt, distilled H2O and detergent jointly called as lysis solution. DNA purification is done by enzymatic debasement of polluting proteins with ethyl alcohol. A spectrophotometer is used in finding the concentration and pureness of the proteins. ( 2 )


    Isolation of Deoxyribonucleic acid from Onion

    The bare-assed onion bulb was chopped and measured homogenized. The sample was placed in a liquidizer added with an ice-cold lysis solution so for 45 seconds at low velocity. Meanwhile, the lysis solution used was prepared beforehand by blending 5.00 milliliter of liquid detergent, 5.00 milliliter of 0.500M EDTA, 10.0 milliliter of 50 % Na Cl solution, and 80 milliliter of distilled H2O and placed in an ice bath. After homogenising, the sample was filtered through the cheesecloth and the gathered filtrate was placed in a 250-ml beaker. A 10.0 milliliter of 5 % pepsin solution was added to the filtrate and placed on an ice bath for 10 proceedingss with occasional stirring. Ice cold 30.0 milliliter of 95 % ethyl alcohol was pipette to the side of the beaker incorporating the sample and base for 10 proceedingss on ice bath. Once the Deoxyribonucleic acid precipitates appeared at the interface of the solution, the Deoxyribonucleic acid was already ready for isolation. The spooled Deoxyribonucleic acid was transferred instantly to a pre-weighed 100-ml beaker to find the mass and percent output of the sample. The stray DNA was added with 10.0 milliliters of 95 % ethyl alcohol so covered with aluminium foil and refrigerated in readying for the following research lab process.

    Word picture of DNA.

    Small sum of DNA sample was placed in a trial tubing added with 1.00 milliliters of 20 % TCA followed by heating the sample for 10 proceedingss in H2O bath with 1.00 milliliters distilled H2O. A 2.00 milliliter of diphenylamine solution was added so heat once more in a H2O bath for 10 proceedingss. The colour alteration was observed and the optical density of the sample from 400 nanometers to 700 nanometer was scanned to find the wavelength of maximal soaking up. Mean while, small sum of the DNA sample was placed in a separate trial tubing filled with 5.00 milliliters distilled H2O and scanned to read the optical density at 260 nm so at 280 nanometer. After finding the A260/A280 value, the sample was heated to boil for 5 proceedingss and read the optical density adain at 260 nanometers.


    The mass of the natural sample gathered from onion is 30.4 g. After homogenisation and adding of pepsin solution and ethyl alcohol, DNA precipitates were became seeable and transferred to another beaker. The stray DNA measures 23 g.

    Percentage Recovery

    Mass or natural sample: 30.4 g

    Mass of stray Deoxyribonucleic acid: 15. 11 g

    Percent Output: 49.70 %

    Word picture of Deoxyribonucleic acid

    Chemical reaction with Diphenylamine

    Color of formed solution: green

    Experimental & A ; Ucirc ; ?max:

    Theoretical & A ; Ucirc ; ? soap:

    Percentage mistake:

    Purity Determination

    Optical density at 250 nanometers: 1.304

    Optical density at 280 nanometers: 1.942

    A260/ A280 value: 0.671

    Denaturation of Deoxyribonucleic acid

    Initial optical density at 260 nanometers: 1.304

    Optical density at 260 nanometers after warming: 1.095

    Percent addition in optical density: 8 %

    Calculation 1. Solution for Percentage Yield Determination

    The deliberate per centum output was rather high. However, still some beginnings of mistake was done while carry oning the experiment, the sample with DNA precipitates was disturbed while reassigning the Deoxyribonucleic acid. The accrued DNA precipitates is adequate for the following process which is word picture.

    Figure 1. Optical density at 700 nanometers

    Heat denaturation of DNA, causes the dual spiral construction to wind off and organize individual stranded Deoxyribonucleic acid. Therefore, the bases unstacked and can absorb more light doing an addition after denaturation. But based on the consequences gathered, the initial optical density at 260 nanometer was 1.304 so was decreased after heating which was 1.095. The deliberate per centum addition in optical density was 8 % . This mistake is possibly, due to the warming procedure. The Deoxyribonucleic acid acquired was rather greater and was non wholly het afterwards doing dual spiral construction non to wind off and organize a individual isolated Deoxyribonucleic acid.

    The filtrate gathered from this experiment was made of onions and lysis solution. Onion was used in this survey due to low amylum content, leting the Deoxyribonucleic acid to be more seeable sing the onion as one of the best beginning of DNA. ( 4 )

    The used of lysis solution was to divide the Deoxyribonucleic acid from excess cell constituents and to maintain the location in which the Deoxyribonucleic acid will non be tainted. The NaCL provides NA+ ions that will blockade the negative charge as of phosphate terminals of DNA. Permiting these terminals to come nigher so they can precipitate out of a cold solution. The detergent causes the interrupting down of the cell membrane by emulsifying the cell proteins and lipoids. Besides, interrupting the polar connexions that jointly holds the cell membrane. The composites formed with these lipoids and proteins causes the precipitate out of solution. Meanwhile, the intent of EDTA is to chelates metal ions. ( 5 ) A Pepsin solution was used for purification via enzymatic debasement.

    Deoxyribonucleic acid is polar due to its highly charged phosphate anchor which makes it soluble in H2O. Thus DNA is indissoluble in ice cold ethyl alcohol, as a consequence when the cold ethyl alcohol was added, it causes stable ionic bonds to organize and precipitate the Deoxyribonucleic acid.

    Heating the sample is the 1 responsible for the formation of the ascertained colour of Deoxyribonucleic acid with diphenylamine. When the Deoxyribonucleic acid is heated with acid, the 2-deoxyribose is converted to w-hydroxylaevulinic aldehyde, which reacts with the compound diphenylamine. Through this, a blue-colored compound supposed to bring forth. In our sample the colour observed was green perchance because of the DNA concentration.

    The ratio of soaking ups at 260 nm V 280 nanometer is often used to measure DNA taint of protein solutions. The nucleic acids, DNA and RNA, absorbs at 260 nanometers and proteins absorb at 280 nanometer. Based on the consequences, the rate ratio of soaking ups at 260 nm V 280 nanometer is 0.671. Since proteins absorb visible radiation at 280 nanometer, the ratio is low intending there is a batch of protein absorbed at 280nm.

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