After running DNA in a gel, bands of different sizes and species might appear. Scientists know silver carp are at North Shore site 1 because one of the bands in lane 1 matches a band in the positive control (Option C).
Gel
When DNA was isolated and run in a gel, many bands migrated to different points.
These bands were the different-sized fragments of DNA samples from different species from the six sites.
Researchers wanted to figure out where the silver carp is.
To do it, they needed to identify the bands on the gel that belonged to the silver carp DNA, so they included negative and positive controls to make comparisons.
Positive and negative Controls
Negative and positive controls guarantee the interpretations of the results.
- The positive control shows the band sizes that belong to the silver carp DNA.
Any band in the sampling sites that matches one of the positive control bands indicates that the species is present at that site.
- The negative control is the opposite. It is the absence of the species' DNA.
Results interpretation
As we can see, there are four sites where the bands match one of the bands of the positive control. These are,
- North shore site 1
- Chicago site 1
- Calumet site 1
- Calumet site 2
This means that at these four sites, the silver carp is present.
So scientists know silver carp are at North Shore site 1 because one of the bands in lane 1 matches a band in the positive control (Option C).
By looking at the lane of the North Shore site 1, we can also see another band (Thinner and grey). But this band does not match either of the positive control bands. This result suggests that the grey band belongs to another species' DNA.
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