Sometimes you’ll find that when you double click on a document (for example a protein sequence) that it opens in the wrong application. Generally this has resulted from recently installing a new application that has registered itself as the default application that you normally use to open that document. This will overwrite your default application.
For example you double click on a Genbank sequence file (that has a file extension ending in “.gb”. You expect to see this sequence in MacVector, but instead it opens in some other application.
Here’s how to fix this:
Now close the Get info dialog and double click on a text file. It should now open in TextEdit.