Part 6 - DNA Sequence Analysis
Sample B - Stool Sample
(See Samples section for more info)
After the sequence information has
been gathered from all the reaction tubes, the computer builds the actual
sequence by matching together different pieces. You now have the 16S rDNA
sequence for this bacterial species, which can be compared with all other
known 16S rDNA sequences for identification.
Learn about the science behind sequence matching.
There are many sequence databases in existence. Some databases are sold
commercially as part of an identification kit. In this example, we will
use the GenBank public database available through the National Library of
Medicine. The matching algorithm is known as BLAST (Basic Local Alignment
Search Tool). A direct match of the DNA sequence determines the exact bacterial
species you have found. When the DNA sequence is not an exact match but
a close match to another found in the sequence database, you need to assess
whether it is a new species or a variation of an existing one.
Learn more about BLAST search results.
Now follow these steps to identify your sample:
Step 1: Click here to see the data
output from the sequencer. Select the all data in the window and
copy (ctrl-c on the PC or cmd-c on the Mac).
Step 2: Click here to open the simulated BLAST search page to perform your search.
(This will pop open a new window)
Step 3: Paste your data (ctrl-v on the PC or cmd-v on the Mac) in
the large field next to where it says search.
Step 4: Click the BLAST button below the search field.
Step 5: Click the Format! button to check the results of the search.
Step 6: Come back to this page (which should remain open) and identify
the bacteria in the lab window to the left.
Click here to perform a live BLAST search.
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