Regular expressions (also known as regex) provide a flexible way to match strings of text, such as particular characters, words, or patterns of characters. Below is an introduction into regex usage in SINETable (actually regex allows much more than shown but too sophisticated patterns make little sense in SINETable).

You can use special characters and wildcards in SINETable search boxes:

Any character, wildcard, or their combination in parentheses can be followed with a repetition:

For instance, 5S   in the Structure box will match SINEs with a 5S rRNA-derived region located anywhere, while ^5S  will match only those with a 5S rRNA-derived region at the 5' end. ^..$   in the Tail box will show tails composed of dinucleotide repeats. .+   matches any character repeated one or more times. Thus, tRNA.LINE   will match SINEs with a tRNA-derived region immediately followed by a LINE-derived region, while tRNA.+LINE   will match SINEs with a LINE-derived region anywhere downstream of a a tRNA-derived region.

Certain characters have special meaning in regex including repetition characters, various brackets, and hyphen. Precede such character in the search pattern with a backslash; e.g., \?\?\?   will match SINEs with a region of unknown origin ('???'). Note that the search is case sensitive, so tc   in the Features box will fail to match SINEs with a (TC)_n stretch; use TC   instead.

Finally, alternative patterns are separated by vertical bar; e.g., (tRNA)|(ANRt)   in the Structure box will match SINEs with tRNA-derived regions in both orientations.

Other examples: