You are to non-culturally detect the presence of E. coli in the soil from a cow pasture. You do this by extracting the total DNA from a sample of the soil and PCR amplifying with E. coli-specific primers that bind to a gene only found in E. coli that amplify a region of the DNA 167 bp long. Propose a postive sample that could be tested alongside your experimental sample.
A. Known Shigella DNA
C. Number of Injections
D. Muscle DNA
E. Known E. coli DNA
I think the answer is (E) Known E. coli DNA. That would be the positive control in this context. For a positive control, you need something that you would know the response for. E. coli specific primers would amplify the known E. coli DNA. Water is obviously wrong. I could be wrong. Am I missing something?
Yes, you're correct. The question is asking for a positive sample that would be amplified by E. coli specific primers. Known E. coli DNA would do the trick.