ISOLATION OF DNA FROM ONIONS 植物 DNA 的粗提

Aim To isolate nucleic acids from onion tissue. Note: nucleic acids prepared in this way will not be very pure

Equipment and materials Water bath, set at 60 ℃ Ice in a jug onion, Washing-up liquid Table salt Protease enzyme Ice cold ethanol

Principle Household detergent is used to degrade both the cell membranes and those surrounding the nuclei. Cell fragments are separated by filtration The nucleic acids and soluble proteins remain Enzyme is used to degrade the proteins Nucleic acid is precipitated into ice cold ethanol

Procedure Add the 3g table salt to the 10cm 3 washing-up liquid Chop the onion into small pieces roughly 5mm x 5mm Add the chopped onion to a beaker with the salty washing-up liquid solution Put the beaker in a water bath at 60 ℃ for exactly 15 minutes Cool the mixture by standing the beaker in an ice water bath for 5 min, stirring frequently

Filter the mixture into a second beaker. Ensure that the foam on top of the liquid does not contaminate the filtrate Add 2-3 drops of protease to about 10 cm 3 of the onion tissue extract and mix well Pour ice cold ethanol carefully down the side of the onion extract Nucleic acids will precipitate at the interface and float into the upper (ethanol)layer

Take some nucleic acids and transfer into TE buffer Incubate in 60 ℃ water-bath for 5-10min Take 10 uL and add 3 uL 6X Load buffer, mix Load to a 0.6% agarose gel, running the gel under the 120 volts for 30min Detect DNA under UV light

assignment Describe what you observed eventually discussion