VariableMeasured using a...
IndependentSize/charge of DNA fragments
DependentDistance the DNA fragments migrate according to charge and size Controlled (validity)1.–Potential difference across the gel
2.–type and source of restriction enzymes that are used to cut the gel
3.–time the nylon membrane is placed on the agarose gel.
Voltmeter/ Electrophoresis machine
Particular type of species
Step (indicate where step ensures/increases validity or reliability) 1) Double stranded DNA is cut into fragments and lengths by restriction enzymes. 2) Place DNA samples into wells at the one end of the gel using a micropipette. Then insert the buffer containing the dye into each of the DNA samples in order to make the sample easier to see.
3) Using the micropipette and a new pipette tip take some of the DNA sample and place into a gel well, repeat this using the DNA size sample. The DNA size sample will act as a control and aid you to measure the DNA strands lengths. The gel is submerged into a buffer solution The buffer should help conduct the electrical current from one end of the gel to the other. Also it will prevent the gel from drying out during the experiment.
4) The DNA has a negative charge and is moved through the gel by plugging in the black end. Air bubbles are coming out of both electrodes, meaning the current is running. The DNA is repelled by the negative charge and moves through the gel towards the positive charge. Shorter strands move through the gel quicker than long strands. 5) A reference sample with added known lengths to compare the base pairs. DNA is transferred to a nylon or nitrocellulose membrane by solution drawn up through the gel called southern blotting. DNA double strands split and stick to the membrane. 6) The membranes are placed into a bag with the DNA probe. The single-stranded DNA probe binds to fragments with a complementary...