Question

1. You have a liquid sample that contains intact phage particles and ruptured bacterial cells.

a. Where would you expect to find DNA in this sample?

b. How can you treat this sample so that at the end of your work you will maximize the yield of phage genome and minimize the yield of potential interfering nucleic acids?

Answer 1

a. As the liquid sample contains intact phage particles and ruptured bacterial cells, the DNA in this sample can be expected to be found in the liquid sample. This DNA that is found in the liquid sample will be of the bacterial cells as the cells are ruptured and the DNA of the bacterial sample is in the liquid. The bacteriophage DNA will be found inside the protein coat of the intact phage particles.

b. To maximize the yield of phage genome, one must first treat the liquid sample with DNAse so that all of the bacterial DNA is degraded and then inactivate the DNAse enzyme. Next the liquid sample needs to be treated with proteases so that the phage particles are ruptured and the phage DNA can be brought into the liquid sample. The protease treatment also degrades the DNAse if any is left after inactivating thereby reducing its activity. Hence by doing this the sample has maximum yield of phage genome and minimum of interfering nucleic acids.

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