EMBOSS: palindrome

Program palindrome ( YMBC , NCHC )


Looks for inverted repeats in a nucleotide sequence


This looks for inverted repeats (stem loops) in a nucleotide sequence.

It will find inverted repeats that include a proportion of mismatches and gaps (bulges in the stem loop).

It works by finding all possible inverted matches satisfying the specified conditions of minimum and maximum length of palindrome, maximum gap between repeated regions and number of mismatches allowed.

Secondary structures like inverted repeats in genomic sequences may be implicated in initiation of DNA replication.


Here is a sample session with palindrome. As there are a number of overlapping possibilties in this sequence, we choose a longer minimum repeat length.

% palindrome
Input sequence: embl:hsts1
Enter minimum length of palindrome [10]: 15
Enter maximum length of palindrome [100]: 
Enter maximum gap between repeated regions [100]: 
Number of mismatches allowed [0]: 
Output file [hsts1.pal]: 
Report overlapping matches [Y]: 

Command line arguments

   Mandatory qualifiers:
  [-insequence]        sequence   Sequence USA
   -minpallen          integer    Enter minimum length of palindrome
   -maxpallen          integer    Enter maximum length of palindrome
   -gaplimit           integer    Enter maximum gap between repeated regions
   -nummismatches      integer    Number of mismatches allowed
  [-outfile]           outfile    Output file name
   -[no]overlap        bool       Report overlapping matches

   Optional qualifiers: (none)
   Advanced qualifiers: (none)
   General qualifiers:
  -help                bool       report command line options. More
                                  information on associated and general
                                  qualifiers can be found with -help -verbose

Mandatory qualifiers Allowed values Default
(Parameter 1)
Sequence USA Readable sequence Required
-minpallen Enter minimum length of palindrome Integer 1 or more 10
-maxpallen Enter maximum length of palindrome Any integer value 100
-gaplimit Enter maximum gap between repeated regions Integer 0 or more 100
-nummismatches Number of mismatches allowed Positive integer 0
(Parameter 2)
Output file name Output file <sequence>.palindrome
-[no]overlap Report overlapping matches Yes/No Yes
Optional qualifiers Allowed values Default
Advanced qualifiers Allowed values Default

Input file format

The input for palindrome is a nucleotide sequence.

Output file format

Here is the output file from the example run:

Palindromes of:  HSTS1 
Sequence length is: 18596 
Start at position: 1
End at position: 18596
Minimum length of Palindromes is: 15 
Maximum length of Palindromes is: 100 
Maximum gap between elements is: 100 
Number of mismatches allowed in Palindrome: 0

126   caaaaaaaaaaaaaaaa   142
217   gtttttttttttttttt   201

127   aaaaaaaaaaaaaaaa   142
215   tttttttttttttttt   200

127   aaaaaaaaaaaaaaaa   142
214   tttttttttttttttt   199

127   aaaaaaaaaaaaaaaa   142
213   tttttttttttttttt   198

127   aaaaaaaaaaaaaaaa   142
212   tttttttttttttttt   197

127   aaaaaaaaaaaaaaaa   142
211   tttttttttttttttt   196

127   aaaaaaaaaaaaaaaa   142
210   tttttttttttttttt   195

127   aaaaaaaaaaaaaaaa   142
209   tttttttttttttttt   194

127   aaaaaaaaaaaaaaaa   142
208   tttttttttttttttt   193

127   aaaaaaaaaaaaaaaa   142
207   tttttttttttttttt   192

127   aaaaaaaaaaaaaaaa   142
206   tttttttttttttttt   191

127   aaaaaaaaaaaaaaaa   142
205   tttttttttttttttt   190

127   aaaaaaaaaaaaaaaagaccgccagggct   155
204   ttttttttttttttttctggcggtcccga   176

Data files



Unless the qualifier '-nooverlap' is specified, palindrome makes no attempt to exclude subsets of previously found palindromes.

Several examples can be seen in the sample output above.


Some references on inverted repeats:
  1. Pearson CE, Zorbas H, Price GB, Zannis-Hadjopoulos M Inverted repeats, stem-loops, and cruciforms: significance for initiation of DNA replication. J Cell Biochem 1996 Oct;63(1):1-22
  2. Waldman AS, Tran H, Goldsmith EC, Resnick MA. q Long inverted repeats are an at-risk motif for recombination in mammalian cells. Genetics. 1999 Dec;153(4):1873-83. PMID: 10581292; UI: 20050682
  3. Jacobsen SE Gene silencing: Maintaining methylation patterns. Curr Biol 1999 Aug 26;9(16):R617-9
  4. Lewis S, Akgun E, Jasin M. Palindromic DNA and genome stability. Further studies. Ann N Y Acad Sci. 1999 May 18;870:45-57. PMID: 10415472; UI: 99343961
  5. Dai X, Greizerstein MB, Nadas-Chinni K, Rothman-Denes LB Supercoil-induced extrusion of a regulatory DNA hairpin. Proc Natl Acad Sci U S A 1997 Mar 18;94(6):2174-9



Diagnostic Error Messages


Exit status

It always exists with a status of 0.

Known bugs


See also

einvertedFinds DNA inverted repeats
equicktandemFinds tandem repeats
etandemLooks for tandem repeats in a nucleotide sequence

einverted also looks for inverted repeats but is much slower and more sensitive, as it finds low-quality (very mismatched) repeats and repeats with gaps.


This application was written by Mark Faller (mfaller@hgmp.mrc.ac.uk)


Written (1999) - Mark Faller.

Target users

This program is intended to be used by everyone and everything, from naive users to embedded scripts.