Question

DNA isolated from water samples collected in six different sites was prepared and analyzed by gel electrophoresis for the presence of carp. The resulting gel is shown. Lanes 1 through 6 contain the DNA from each site. Lanes 7 and 8 represent the negative and positive controls.
Based on the banding patterns, how many sites tested positive for carp?

Answer 1

If lane 7 represent the negative control and 8 shows the positive controls (as we may infer by reading that lanes 7 and 8 represent negative and positive controls RESPECTIVELY) then we can say that lanes 1,3,5,6 and 8 tested positive for carp. 

Answer 2

Gel electrophoresis can be defined as the process of separation of the macro-molecules  and the fragments based on their charge and size. In the gel electrophoresis given, the lane 7 indicates the negative control, and the lane 8 indicates the positive control. The bands formed in the lanes 1,3,5, and 6 corresponds to the ban in the lane 8, which is a positive control. Hence, based on these observations, it can be said that a total of 4 sites tested positive for carp.