They would use random primers. A DNA hexamer (six-base sequence) is sufficiently long to serve as a PCR primer, but short enough that it would take only 4096 different types of molecule to comprise all possible sequences. Of course, we don't want the sample DNA to be plastered in our primers, so we'll pare those 4096 down to a handful, at least one of which, in any sample sequence of significant length, will nonetheless find somewhere to anneal. Once we've gone through enough cycles, it's likely that we'll have amplified at least some segment of the sample DNA. Then, getting the reaction contents purified and sequenced is simply a matter of applied microfluidics.
Back in the 70's, NASA ran an experiment on one of the Viking landers to try to see if there was any life on Mars. The experiment contained some radiolabeled "food," to which a sample of regolith and water would be added. If radiolabeled gas evolved from the resulting mixture and was detected, it would be taken as a sign that some kind of native microbe was eating the food and emitting the gas as a byproduct of anaerobic respiration. And in fact, the experiment did detect radiolabeled gas. However, none of the other analyses turned up positive, including the mass spectrometer. So scientists floated an alternative theory: that the Martian regolith contained some kind of oxidizing agent, which would have explained both the evolution of radiolabeled gas, and the absence of life on Mars. Most scientists accepted this theory, but even to this day, there were a few who believed it was a little bit too convenient, and that the labeled release experiment had actually turned up evidence of life. The discovery of perchlorate, a strong oxidizing agent, would put that speculation to rest.
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They would use random primers. A DNA hexamer (six-base sequence) is sufficiently long to serve as a PCR primer, but short enough that it would take only 4096 different types of molecule to comprise all possible sequences. Of course, we don't want the sample DNA to be plastered in our primers, so we'll pare those 4096 down to a handful, at least one of which, in any sample sequence of significant length, will nonetheless find somewhere to anneal. Once we've gone through enough cycles, it's likely that we'll have amplified at least some segment of the sample DNA. Then, getting the reaction contents purified and sequenced is simply a matter of applied microfluidics.
Back in the 70's, NASA ran an experiment on one of the Viking landers to try to see if there was any life on Mars. The experiment contained some radiolabeled "food," to which a sample of regolith and water would be added. If radiolabeled gas evolved from the resulting mixture and was detected, it would be taken as a sign that some kind of native microbe was eating the food and emitting the gas as a byproduct of anaerobic respiration. And in fact, the experiment did detect radiolabeled gas. However, none of the other analyses turned up positive, including the mass spectrometer. So scientists floated an alternative theory: that the Martian regolith contained some kind of oxidizing agent, which would have explained both the evolution of radiolabeled gas, and the absence of life on Mars. Most scientists accepted this theory, but even to this day, there were a few who believed it was a little bit too convenient, and that the labeled release experiment had actually turned up evidence of life. The discovery of perchlorate, a strong oxidizing agent, would put that speculation to rest.