DNA Analysis (Advanced) – Counting the STR’s

When you select a control sample or piece of evidence to examine, all 20 of the STR’s for that sample will be presented. However, to complete the lab, you only have to count the STR’s at two of the STR locations in the DNA chain.

These are STR D3S1358 and STR CSF1PO. (They are highlighted in light blue for easy recognition.)

The first STR location, D3S1358, is open by default so you can view the repeat patterns of nucleaotides at that location.

First select Show Only STRs to make it easier to focus your attention only at the STRs.

Then select the Counting Tool to make it easier to count the repeat patterns at this location.

With your cursor, select the gray slider and slide it to the right. As the repeat patterns slide past the counter, they are counted on both Chromatid #1 and Chromatid #2.

Based on your findings and analysis, answer the lab questions for this STR location on zygosity, pattern type and the number of repeat patterns.

Do the same analysis for the second STR in the lab – CSF1PO. (To get started at this STR, first click on Show DNA, then follow the same steps as above.)