Ewan Birney


Bio::Seq - Sequence object, with features


    $seqio  = Bio::SeqIO->new ( '-format' => 'embl' , -file => 'myfile.dat');
    $seqobj = $seqio->next_seq();

    # features must implement Bio::SeqFeatureI

    @features = $seqobj->top_SeqFeatures(); # just top level
    @features = $seqobj->all_SeqFeatures(); # descend into sub features

    $seq      = $seqobj->seq(); # actual sequence as a string
    $seqstr   = $seqobj->subseq(10,50);
    $ann      = $seqobj->annotation(); # annotation object


A Seq object is a sequence with sequence features placed on them. The Seq object contains a PrimarySeq object for the actual sequence and also implements its interface.

In bioperl we have 3 main players that people are going to use

  Bio::PrimarySeq - just the sequence and its names, nothing else.
  Bio::SeqFeatureI - a location on a sequence, potentially with a sequence.
                    and annotation
  Bio::Seq        - A sequence and a collection of seqfeatures (an aggregate) with
                    its own annotation.

Although bioperl is not tied to file formats heavily, these distinctions do map to file formats sensibly and for some bioinformaticians this might help you:

  Bio::PrimarySeq - Fasta file of a sequence
  Bio::SeqFeatureI - A single entry in an EMBL/GenBank/DDBJ feature table
  Bio::Seq        - A single EMBL/GenBank/DDBJ entry

By having this split we avoid alot of nasty ciricular references (seqfeatures can hold a reference to a sequence without the sequence holding a reference to the seqfeature).

Ian Korf really helped in the design of the Seq and SeqFeature system.


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AUTHOR - Ewan Birney, inspired by Ian Korf objects

Email birney@sanger.ac.uk

Describe contact details here


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


 Title   : new
 Usage   : $seq    = Bio::Seq->new( -seq => 'ATGGGGGTGGTGGTACCCT',
                                    -id  => 'human_id',
                                    -accession_number => 'AL000012',

 Function: Returns a new seq object from
           basic constructors, being a string for the sequence
           and strings for id and accession_number
 Returns : a new Bio::Seq object

PrimarySeq interface

The primaryseq interface is the basic sequence getting and setting methods found on all sequences.

These methods implement the PrimarySeq interface by delegating to the primary_seq inside the object. This means that you can use a Seq object wherever there is a PrimarySeq, and of course, you are free to use these functions anyway.


 Title   : seq
 Usage   : $string    = $obj->seq()
 Function: Returns the sequence as a string of letters. The
           case of the letters is left up to the implementer.
           Suggested cases are upper case for proteins and lower case for
           DNA sequence (IUPAC standard),
           but implementations are suggested to keep an open mind about
           case (some users... want mixed case!)
 Returns : A scalar


 Title   : length
 Usage   : $len = $seq->length()
 Example :
 Returns : integer representing the length of the sequence.
 Args    :


 Title   : subseq
 Usage   : $substring = $obj->subseq(10,40);
 Function: returns the subseq from start to end, where the first base
           is 1 and the number is inclusive, ie 1-2 are the first two
           bases of the sequence

           Start cannot be larger than end but can be equal

 Returns : a string
 Args    :


 Title   : display_id
 Usage   : $id_string = $obj->display_id($newid);
 Function: returns or sets the display id, aka the common name of the
           Sequence object.

           The semantics of this is that it is the most likely string
           to be used as an identifier of the sequence, and likely to
           have "human" readability.  The id is equivalent to the ID
           field of the GenBank/EMBL databanks and the id field of the
           Swissprot/sptrembl database. In fasta format, the >(\S+) is
           presumed to be the id, though some people overload the id
           to embed other information. Bioperl does not use any
           embedded information in the ID field, and people are
           encouraged to use other mechanisms (accession field for
           example, or extending the sequence object) to solve this.

           Notice that $seq->id() maps to this function, mainly for
           legacy/convience issues
 Returns : A string
 Args    : newid (optional)


 Title   : accession_number
 Usage   : $unique_biological_key = $obj->accession_number;
 Function: Returns the unique biological id for a sequence, commonly
           called the accession_number. For sequences from established
           databases, the implementors should try to use the correct
           accession number. Notice that primary_id() provides the
           unique id for the implemetation, allowing multiple objects
           to have the same accession number in a particular implementation.

           For sequences with no accession number, this method should return
 Returns : A string
 Args    : None


 Title   : desc
 Usage   : $seqobj->desc()
 Function: Sets/Gets the description of the sequnce
 Example :
 Returns :
 Args    :


 Title   : primary_id
 Usage   : $unique_implementation_key = $obj->primary_id;
 Function: Returns the unique id for this object in this
           implementation. This allows implementations to manage
           their own object ids in a way the implementaiton can control
           clients can expect one id to map to one object.

           For sequences with no natural id, this method should return
           a stringified memory location.

           Also notice that this method is B<not> delegated to the
           internal PrimarySeq object
 Returns : A string
 Args    : None


 Title   : can_call_new
 Usage   : if( $obj->can_call_new ) {
             $newobj = $obj->new( %param );
 Function: can_call_new returns 1 or 0 depending
           on whether an implementation allows new
           constructor to be called. If a new constructor
           is allowed, then it should take the followed hashed
           constructor list.

           $myobject->new( -seq => $sequence_as_string,
                           -display_id  => $id
                           -accession_number => $accession
                           -moltype => 'dna',
 Example :
 Returns : 1 or 0
 Args    :


 Title   : moltype
 Usage   : if( $obj->moltype eq 'dna' ) { /Do Something/ }
 Function: Returns the type of sequence being one of
           'dna', 'rna' or 'protein'. This is case sensitive.

           This is not called <type> because this would cause
           upgrade problems from the 0.5 and earlier Seq objects.

 Returns : a string either 'dna','rna','protein'. NB - the object must
           make a call of the type - if there is no type specified it
           has to guess.
 Args    : none

Methods provided in the Bio::PrimarySeqI interface

These methods are inherited from the PrimarySeq interface and work as one expects, building new Bio::Seq objects or other information as expected.

Sequence Features are not transfered to the new objects. This is possibly a mistake. Anyone who feels the urge in dealing with this is welcome to give it a go.


 Title   : revcom
 Usage   : $rev = $seq->revcom()
 Function: Produces a new Bio::Seq object which
           is the reversed complement of the sequence. For protein
           sequences this throws an exception of "Sequence is a protein. Cannot revcom"

           The id is the same id as the orginal sequence, and the accession number
           is also indentical. If someone wants to track that this sequence has be
           reversed, it needs to define its own extensions

           To do an inplace edit of an object you can go:

           $seq = $seq->revcom();

           This of course, causes Perl to handle the garbage collection of the old
           object, but it is roughly speaking as efficient as an inplace edit.

 Returns : A new (fresh) Bio::Seq object
 Args    : none


 Title   : trunc
 Usage   : $subseq = $myseq->trunc(10,100);
 Function: Provides a truncation of a sequence,

 Example :
 Returns : a fresh Bio::Seq object
 Args    :


 Title   : id
 Usage   : $id = $seq->id()
 Function: This is mapped on display_id
 Example :
 Returns :
 Args    :

Seq only methods

These methods are specific to the Bio::Seq object, and not found on the Bio::PrimarySeq object


 Title   : primary_seq
 Usage   : $obj->primary_seq($newval)
 Example :
 Returns : value of primary_seq
 Args    : newvalue (optional)
 Throws  : Bio::Root::BadParameter if the supplied argument does
           not derive from Bio::PrimarySeqI.


 Title   : annotation
 Usage   : $obj->annotation($seq_obj)
 Example :
 Returns : value of annotation
 Args    : newvalue (optional)


 Title   : add_SeqFeature
 Usage   : $seq->add_SeqFeature($feat);
 Function: Adds the given feature object (or each of an array of feature
           objects to the feature array of this
           sequence. The object passed is required to implement the
           Bio::SeqFeatureI interface.
 Example :
 Returns : TRUE on success
 Args    : A Bio::SeqFeatureI implementing object, or an array of such objects.
 Throws  : Bio::Root::BadParameter if any of the supplied arguments do
           not derive from Bio::SeqFeatureI.


 Title   : top_SeqFeatures
 Usage   : @feat_ary = $seq->top_SeqFeatures();
 Function: Returns the array of top-level features for this sequence object.
           Features which are not top-level are subfeatures of one or more
           of the returned feature objects, which means that you must
           traverse the subfeature arrays of each top-level feature object
           in order to traverse all features associated with this sequence.

           Use all_SeqFeatures() if you want the feature tree flattened into
           one single array.
 Example :
 Returns : An array of Bio::SeqFeatureI implementing objects.
 Args    :


 Title   : all_SeqFeatures
 Usage   : @feat_ary = $seq->all_SeqFeatures();
 Function: Returns the tree of feature objects attached to this sequence
           object flattened into one single array. Top-level features will
           still contain their subfeature-arrays, which means that you
           will encounter subfeatures twice if you traverse the subfeature
           tree of the returned objects.

           Use top_SeqFeatures() if you want the array to contain only the
           top-level features.
 Example :
 Returns : An array of Bio::SeqFeatureI implementing objects.
 Args    :


 Title   : feature_count
 Usage   : $seq->feature_count()
 Function: Return the number of SeqFeatures attached to a sequence
 Example :
 Returns : number of SeqFeatures
 Args    : none


 Title   : species
 Usage   :
 Function: Gets or sets the species
 Example : $species = $self->species();
 Returns : Bio::Species object
 Args    : Bio::Species object or none;