Christopher Fields > BioPerl > Bio::Seq::PrimedSeq



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Bio::Seq::PrimedSeq - A sequence and a pair of primers matching on it


  use Bio::Seq;
  use Bio::Seq::PrimedSeq;

  my $template = Bio::Seq->new( -seq => 'AGCTTTTCATTCTGACTGCAAC' );
  my $left     = Bio::Seq->new( -seq => 'AGCT' );
  my $right    = Bio::Seq->new( -seq => 'GTTGC' );

  my $primedseq = Bio::Seq::PrimedSeq->new(
          -seq          => $template,  # sequence object
          -left_primer  => $left,      # sequence or primer object
          -right_primer => $right      # sequence or primer object

  # Get the primers as Bio::SeqFeature::Primer objects
  my @primer_objects = $primedseq->get_primer();

  # Sequence object representing the PCR product, i.e. the section of the target
  # sequence contained between the primers (primers included)
  my $amplicon_seq = $primedseq->amplicon();

  print 'Got amplicon sequence: '.$amplicon_seq->seq."\n";
  # Amplicon should be: agctTTTCATTCTGACTgcaac


This module was created to address the fact that a primer is more than a SeqFeature and that there is a need to represent the primer-sequence complex and the attributes that are associated with the complex.

A PrimedSeq object is initialized with a target sequence and two primers. The location of the primers on the target sequence is calculated if needed so that one can then get the PCR product, or amplicon sequence. From the PrimedSeq object you can also retrieve information about melting temperatures and what not on each of the primers and the amplicon. The Bio::Tools::Primer3 module uses PrimedSeq objects extensively.

Note that this module does not simulate PCR. It assumes that the primers will match in a single location on the target sequence and does not understand degenerate primers.

Bio::Seq::PrimedSeq was initially started by Chad Matsalla, and later improved on by Rob Edwards.


  1. Run Primer3 to get PrimedSeq objects:
      use Bio::SeqIO;
      use Bio::Tools::Run::Primer3;
      # Read a target sequences from a FASTA file
      my $file = shift || die "Need a file to read";
      my $seqin = Bio::SeqIO->new(-file => $file);
      my $seq = $seqin->next_seq;
      # Use Primer3 to design some primers
      my $primer3 = Bio::Tools::Run::Primer3->new(-seq => $seq);
      my $results = $primer3->run; # default parameters
      # Write all the results in a Genbank file
      my $seqout = Bio::SeqIO->new(-file => ">primed_sequence.gbk", 
                                   -format => 'genbank');
      while (my $primedseq = $results->next_primer) {
         $seqout->write_seq( $primedseq->annotated_seq );
  2. Create a genbank file for a sequence and its cognate primers:
      use Bio::SeqIO;
      use Bio::Seq::PrimedSeq;
      # Read a FASTA file that contains the target sequence and its two primers
      my $file = shift || die "$0 <file>";
      my $seqin = Bio::SeqIO->new(-file => $file);
      my ($template, $leftprimer, $rightprimer) = 
            ($seqin->next_seq, $seqin->next_seq, $seqin->next_seq);
      # Set up a PrimedSeq object
      my $primedseq = Bio::Seq::PrimedSeq->new(-seq => $template, 
                                               -left_primer => $leftprimer,
                                               -right_primer => $rightprimer);
      # Write the sequences in an output Genbank file
      my $seqout = Bio::SeqIO->new(-file => ">primed_sequence.gbk",
                                   -format => 'genbank');


User feedback is an integral part of the evolution of this and other Bioperl modules. Send your comments and suggestions preferably to one of the Bioperl mailing lists. Your participation is much appreciated.                  - General discussion  - About the mailing lists


Please direct usage questions or support issues to the mailing list:

rather than to the module maintainer directly. Many experienced and reponsive experts will be able look at the problem and quickly address it. Please include a thorough description of the problem with code and data examples if at all possible.

Reporting Bugs

Report bugs to the Bioperl bug tracking system to help us keep track the bugs and their resolution. Bug reports can be submitted via the web:


Rob Edwards,

Based on a module written by Chad Matsalla,


The rest of the documentation details each of the object methods. Internal methods are usually preceded with a _


 Title   : new()
 Usage   : my $primedseq = Bio::SeqFeature::Primer->new( 
                            -seq => $sequence,
                            -left_primer => $left_primer,
                            -right_primer => $right_primer
 Function: Construct a primed sequence.
 Returns : A Bio::Seq::PrimedSeq object
 Args    :  -seq => a Bio::Seq object (required)
            -left_primer => a Bio::SeqFeature::Primer or sequence object (required)
            -right_primer => a Bio::SeqFeature::Primer or sequence object (required)

           If you pass a sequence object to specify a primer, it will be used to
           construct a Bio::SeqFeature::Primer that you can retrieve with the
           L<get_primer> method.

           Many other parameters can be included including all of the output
           parameters from the primer3 program (see L<Bio::Tools::Primer3>). At
           the moment these parameters will simply be stored and do anything.


 Title   : get_primer();
 Usage   :  my @primers = $primedseq->get_primer();
            my $primer = $primedseq->get_primer('-left_primer');
 Function: Get the primers associated with the PrimedSeq object.
 Returns : A Bio::SeqFeature::Primer object
 Args    : For the left primer, use: l, left, left_primer or -left_primer
           For the right primer, use: r, right, right_primer or -right_primer
           For both primers [default], use: b, both, both_primers or -both_primers


 Title   : annotated_sequence
 Usage   : my $annotated_sequence_object = $primedseq->annotate_sequence();
 Function: Get an annotated sequence object containg the left and right 
 Returns : An annotated sequence object or 0 if not defined.
 Args    : 
 Note    : Use this method to return a sequence object that you can write
           out (e.g. in GenBank format). See the example above.


 Title   : amplicon
 Usage   : my $amplicon = $primedseq->amplicon();
 Function: Retrieve the amplicon as a sequence object. The amplicon sequnce is
           only the section of the target sequence between the primer matches
           (primers included).
 Returns : A Bio::Seq object. To get the sequence use $amplicon->seq
 Args    : None
 Note    : 


 Title   : seq
 Usage   : my $seqobj = $primedseq->seq();
 Function: Retrieve the target sequence as a sequence object
 Returns : A seq object. To get the sequence use $seqobj->seq
 Args    : None
 Note    : 


 Title   : _place_primers
 Usage   : $self->_place_primers();
 Function: An internal method to place the primers on the sequence and 
           set up the ranges of the sequences
 Returns : Nothing
 Args    : None
 Note    : Internal use only
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