Probe Match - Help

:: Overview of Probe Match

Probe Match allows you to search the RDP's collection of 16S rRNA sequences using a probe of your choice. This tool will not design probes for you; you will need a third party program such as PRIMROSE to do this.

Probe Match is used in 2 or 3 steps:

:: Probe Search Page

start screenshot

Probes must conform to the following specifications:

Ambiguity codons in your probe will expand to match all associated bases (ie, an 'N' in your probe will match any base). If you specify your probe as targeting the minus strand of the 16S rRNA gene, your probe will be reverse-complemented before searching. Specifing an E.coli region will restrict your search to only those sequences that have data within that region. E.coli region information is obtained from the RDP alignment. This option can be useful if you are interested in what a probe fails to hit. For example, many 'universal' probes will fail to match more than half the available sequences. This is because most of the sequences in the RDP database are partial sequences, and may or may not contain sequence data in the region the probe targeted.

:: Hierarchy View

Probe Match displays your probe hits in the RDP's Hierarchy.

lineage screenshot

hierarchy screenshot

 Hierarchy View Options

Display Depth: Display Depth controls the number of ranks (nodes) displayed in the hierarchy. With the default 'Auto' setting, the program automatically adjusts the depth to display a reasonable number of lines in the hierarchy view. Increase the depth to see more ranks at the same time. Nodes that are grayed out because no probe hits were found in them will not be expanded.

Allowed Errors or Edit Distance: Errors are a mismatch, insert, or delete that occurs when matching a probe to a sequence. The number of errors of these sort that occur when matching a probe to a sequence is called the Edit Distance.

You can change the maximum allowed edit distance using the 'Allow Errors' menu on the results page. The maximum edit distance is 1 + 10% the length of your probe. This maximum is arbitrarily set and has no biological meaning. If there are no other choices available under the 'Allow Errors' menu, this means there were no matches with that many errors.

Data Set Options: Data Set Options alters the types of sequences for which probe hits are displayed.

options screenshot

:: List View

The List View shows your probe hits in a list format.

list screenshot

  1. The first column is the RDP Sequence ID of a sequence that matched your probe. Clicking the sequence ID will take you to its GenBank-formatted RDP sequence record.

  2. If you have selected to allow errors, the second column is the number of mismatches, inserts, or deletes that occurred between the probe and target sequence.
  3. The third column contains the alignment region where the sequence hit. Errors are highlighted in red. It is possible that a probe can match to multiple regions in a sequence. In such cases, only the first and best match is displayed.

  4. The final column is a short description of the sequence.

Clicking on any of the sequences in the Lineage list will return you to that node in the Hierarchy View.

lineage/list screenshot

The Download button will allow you to download a text version of what is displayed. Only sequences under the currently selected node will be downloaded.

download file screenshot

 List View Options

List View Options are the same as the Hierarchy View Options.



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