Investigating CSI – Background material Table of Contents I ...
Investigating CSI – Background material Table of Contents I ...
Investigating CSI – Background material Table of Contents I ...
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For example, in the first loci (which spans the region from 100-150 base pairs)<br />
the victim could have 15 sequence repeats from her mother and 16 from her<br />
father, while, the suspect could have 20 repeats from his mother and 18 from his<br />
father. The PCR reaction with the fluorescein-labeled primers would have<br />
attached tags onto each length <strong>of</strong> repeats. When the sample is run through<br />
electrophoresis, the fluorescein tag would be illuminated, and a reading would be<br />
taken. As we know, smaller samples run faster through electrophoresis, thus the<br />
lane containing the victim’s DNA (which contains some 15-repeat segments and<br />
some 16-repeat segments) would fluoresce and give a reading before the lane<br />
containing the suspect’s DNA (containing 18- and 20-repeat segments).<br />
The victim’s results would show two peaks for the first loci, one at 15 and one at<br />
16. The suspect’s results would also show two peaks for the first loci, but they<br />
would be at 18 and 20. Each <strong>of</strong> the five loci shown above would contain two<br />
peaks for both the victim’s results and the suspect’s results.<br />
………………………………………………………………….<br />
100 120 140 160<br />
15<br />
16<br />
…………………………………………………………………..<br />
100 120 140 160<br />
18<br />
52<br />
20<br />
Victim’s results<br />
Suspect’s<br />
results