Question

Question 1
What positive control reaction could you use to be sure that enough good quality DNA was obtained for a successful PCR reaction from your red or pink flower (the untransformed plant)?
Note: a positive control gives a positive (not negative) result, so you need a reaction that will give you a PCR band when you use DNA from pink or red carnations. A positive control is important because, impurities in DNA preparations are common and can inhibit Taq polymerase. Therefore, in the PCR experiment performed in this practical, we cannot be sure that the negative result (no PCR band) in the pink and red carnations is because these plants lack the transgene, it could be that the DNA is not of sufficient quality for amplification (or it is too concentrated).

Answer 1

The genes that are being studied by PCR should have been sequenced earlier. These sequenced genes should be inserted into a vector and this vector with the insert should be used as the positive control as this vector isolated DNA will have the gene under study and also wont be having the DNA impurities which will be present in common in the samples. Hence a vector with the gene of interest insert should be used as the positive control. This positive control will be amplified by the same primers which amplify the DNA from samples.

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