Sleps in DAR exirochuin Exerciue 12: DNA Estraction 107 strong anionic descrgeot

Question

Sleps in DAR exirochuin Exerciue 12: DNA Estraction 107 strong anionic descrgeot, at a high tomperature (around 72C). This diosohves the nuclear mcmbranes, relcasin g the nuclear DNA into solation(The SDS also inhibits nucleases. This DNA solution contains large numbers of proteins, many of wich cas associate with the DNA then it is precipitated. Proteins can be taken out of a DNA solation by extracting with an oeganic sol will partition into the organic phase whilc vent such as chloroform. Most of the consaminating the e DNA remains in the aqucous phase. Aternatively, the cootaminating proteins can be removed by "salting out." This involves adding a c This causes uch as ammonium acetate to a high concentrat the protcins to come out of solution; they can then be pelleted by centrifugation. After prosein contaminanes have been removed, DNA may be precipitated out of solution by the add tion of an sach as cthanol or isopropanol. The longer the DNA is, the lower its solability in akcohol readily it will precipitate when akcohol is added. In addition, the higher the concentration of is in the solution, the casicr it i carcfiully, our genomic DNA and the more to precipitate. If the procedure in followed large fragments and in high conceneration and thus be readily precipitable with ethanol should be in B. Determination of DNA Concentration DNA absorbs ultraviolet light between 250 and 280 am due to the presence of the ring structures of the purine and pyrimidine bases. It also can be the basis for measuring the concentration of DNA in aqueous solution. For most double stranded DNAs, an absorbance of 1 at 260 nm is equivalent to a grams per milliliter. Thus, to estimate the DNA concentration of a sample, we concentration of 50 micro measure its ODse in a spectrophoto neter and multiply the reading by So,g/mL- Materials lGreen peas Meat tenderizer Dish detergent Table salt Ice cold water Ice cold Ethanol Blender Cheese cloth Small glass beaker Test tube rack Glass rod Glass test tubes Procedure With the help of your instructor, add the following items to a blender: ½ cup ofsplit peas 18 teaspoon of salt I cup cold water 1. Blend for 15 seconds, but be sure not to completely liquefy. Why do we need to blend the peas (Hint: Think about a unique feature that plant cells have in comparison to animal cells.) CE ( 2. What is the purpose of the salt in this mixture? (Hint: Think about the charges of both the DNA molecule and the salt molecule. Look at an image of DNA paying particular attention to the phos- phate groups.)

Explanation / Answer

1. Peas are seed of pea plant. We all know that plant cells have cell-wall where as animal cells haven't any cell wall. Cell wall is a rigid structure in comparison with cell membrane. So, if we don't blande the peas the cell walls will no be braked and the cells with in the peas will not be separated from each other. Hence, we need to blend the peas.

2. The table salt (NaCl) dissociates in aquas medium and donates Na+ and Cl- ions. We all know that DNA is negatively charged in aqueous medium for its phosphate (PO4=) group. For the chage, the DNA molecules contain, it can be easily dissolved in water. So the Na+ ions of salt bind with the DNA stabilised the DNA. So in alcoholic medium we can easily get the separated DNA molecules.

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