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Bio-EnsEMBL-113.0.0
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/ Bio::EnsEMBL::BaseAlignFeature

LICENSE

Copyright [1999-2015] Wellcome Trust Sanger Institute and the EMBL-European Bioinformatics Institute Copyright [2016-2024] EMBL-European Bioinformatics Institute

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

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CONTACT

Please email comments or questions to the public Ensembl
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NAME

Bio::EnsEMBL::BaseAlignFeature - Baseclass providing a common abstract implmentation for alignment features

SYNOPSIS

my $feat = new Bio::EnsEMBL::DnaPepAlignFeature(
  -slice        => $slice,
  -start        => 100,
  -end          => 120,
  -strand       => 1,
  -hseqname     => 'SP:RF1231',
  -hstart       => 200,
  -hend         => 220,
  -analysis     => $analysis,
  -cigar_string => '10M3D5M2I',
  -align_type   => 'ensembl'
);

where $analysis is a Bio::EnsEMBL::Analysis object.

Alternatively if you have an array of ungapped features:

  my $feat =
    new Bio::EnsEMBL::DnaPepAlignFeature( -features => \@features );

where @features is an array of Bio::EnsEMBL::FeaturePair objects.

There is a method to (re)create ungapped features from the cigar_string:

  my @ungapped_features = $feat->ungapped_features();

where @ungapped_features is an array of Bio::EnsEMBL::FeaturePair's.

Bio::EnsEMBL::BaseAlignFeature inherits from:
  Bio::EnsEMBL::FeaturePair, which in turn inherits from:
    Bio::EnsEMBL::Feature,
thus methods from both parent classes are available.


The cigar_string is a condensed representation of the matches and gaps
which make up the gapped alignment (where CIGAR stands for
Concise Idiosyncratic Gapped Alignment Report).

CIGAR format is: n <matches> [ x <deletes or inserts> m <matches> ]*
where M = match, D = delete, I = insert; n, m are match lengths;
x is delete or insert length.

Spaces are omitted, thus: "23M4I12M2D1M"
as are counts for any lengths of 1, thus 1M becomes M: "23M4I12M2DM"


To make things clearer this is how a blast HSP would be parsed:

>AK014066
       Length = 146

  Minus Strand HSPs:

  Score = 76 (26.8 bits), Expect = 1.4, P = 0.74
  Identities = 20/71 (28%), Positives = 29/71 (40%), Frame = -1

Query:   479 GLQAPPPTPQGCRLIPPPPLGLQAPLPTLRAVGSSHHHP*GRQGSSLSSFRSSLASKASA 300
             G  APPP PQG R   P P G + P   L             + + ++  R  +A   +
Sbjct:     7 GALAPPPAPQG-RWAFPRPTG-KRPATPLHGTARQDRQVRRSEAAKVTGCRGRVAPHVAP 64

Query:   299 SSPHNPSPLPS 267
                H P+P P+
Sbjct:    65 PLTHTPTPTPT 75

The alignment goes from 479 down to 267 in the query sequence on the reverse
strand, and from 7 to 75 in the subject sequence.

The alignment is made up of the following ungapped pieces:

query_seq start 447 , sbjct_seq hstart  7 , match length  33 , strand -1
query_seq start 417 , sbjct_seq hstart 18 , match length  27 , strand -1
query_seq start 267 , sbjct_seq hstart 27 , match length 147 , strand -1

When assembled into a DnaPepAlignFeature where:
  (seqname, start, end, strand) refer to the query sequence,
  (hseqname, hstart, hend, hstrand) refer to the subject sequence,
these ungapped pieces are represented by the cigar string:
  33M3I27M3I147M
with start 267, end 479, strand -1, and hstart 7, hend 75, hstrand 1.

CAVEATS

AlignFeature cigar strings have the opposite 'sense'
('D' and 'I' swapped) compared with Exonerate cigar strings.

Exonerate modules in Bio::EnsEMBL::Analysis use this convention:

 The longer genomic sequence specified by:
    exonerate:    target
    AlignFeature: (sequence, start, end, strand)

 A shorter sequence (such as EST or protein) specified by:
    exonerate:    query
    AlignFeature: (hsequence, hstart, hend, hstrand)

The resulting AlignFeature cigar strings have 'D' and 'I'
swapped compared with the Exonerate output, i.e.:

  exonerate:    M 123 D 1 M 11 I 1 M 39
  AlignFeature: 123MI11MD39M

METHODS

new

Arg [..]   : List of named arguments. (-cigar_string , -features, -align_type) defined
             in this constructor, others defined in FeaturePair and 
             SeqFeature superclasses.  Either cigar_string or a list
             of ungapped features should be provided - not both.
Example    : $baf = new BaseAlignFeatureSubclass(-cigar_string => '3M3I12M', -align_type => 'ensembl');
Description: Creates a new BaseAlignFeature using either a cigar string or
             a list of ungapped features.  BaseAlignFeature is an abstract
             baseclass and should not actually be instantiated - rather its
             subclasses should be.
Returntype : Bio::EnsEMBL::BaseAlignFeature
Exceptions : thrown if both feature and cigar string args are provided
             thrown if neither feature nor cigar string args are provided
             warn if cigar string is provided without cigar type
Caller     : general
Status     : Stable

cigar_string

Arg [1]    : string $cigar_string
Example    : $feature->cigar_string( "12MI3M" );
Description: get/set for attribute cigar_string.
             cigar_string describes the alignment:
               "xM" stands for x matches (or mismatches),
               "xI" for x inserts into the query sequence,
               "xD" for x deletions from the query sequence
               where the query sequence is specified by (seqname, start, ...)
               and the subject sequence by (hseqname, hstart, ...).
             An "x" that is 1 can be omitted.
             See the SYNOPSIS for an example.
Returntype : string
Exceptions : none
Caller     : general
Status     : Stable

align_type

Arg [1]    : type $align_type
Example    : $feature->align_type( "ensembl" );
Description: get/set for attribute align_type.
             align_type specifies which cigar string 
             is used to describe the alignment:
             The default is 'ensembl'
Returntype : string
Exceptions : none
Caller     : general
Status     : Stable

alignment_length

Arg [1]    : None
Description: return the alignment length (including indels) based on the alignment_type ('ensembl', 'mdtag')
Returntype : int
Exceptions : 
Caller     : 
Status     : Stable

_ensembl_cigar_alignment_length

Arg [1]    : None
Description: return the alignment length (including indels) based on the cigar_string
Returntype : int
Exceptions :
Caller     :
Status     : Stable

ungapped_features

Args       : none
Example    : @ungapped_features = $align_feature->get_feature
Description: converts the internal cigar_string into an array of
             ungapped feature pairs
Returntype : list of Bio::EnsEMBL::FeaturePair
Exceptions : cigar_string not set internally
Caller     : general
Status     : Stable

strands_reversed

 Arg [1]    : int $strands_reversed
 Description: get/set for attribute strands_reversed
              0 means that strand and hstrand are the original strands obtained
                from the alignment program used
              1 means that strand and hstrand have been flipped as compared to
                the original result provided by the alignment program used.
                You may want to use the reverse_complement method to restore the
                original strandness.
 Returntype : int
 Exceptions : none
 Caller     : general
 Status     : Stable

reverse_complement

Args       : none
Description: reverse complement the FeaturePair based on the cigar type
             modifing strand, hstrand and cigar_string in consequence
Returntype : none
Exceptions : none
Caller     : general
Status     : Stable

_ensembl_reverse_complement

Args       : none
Description: reverse complement the FeaturePair for ensembl cigar string,
             modifing strand, hstrand and cigar_string in consequence
Returntype : none
Exceptions : none
Caller     : general
Status     : Stable

transform

Arg  1     : String $coordinate_system_name
Arg [2]    : String $coordinate_system_version
Example    : $feature = $feature->transform('contig');
             $feature = $feature->transform('chromosome', 'NCBI33');
Description: Moves this AlignFeature to the given coordinate system.
             If the feature cannot be transformed to the destination 
             coordinate system undef is returned instead.
Returntype : Bio::EnsEMBL::BaseAlignFeature;
Exceptions : wrong parameters
Caller     : general
Status     : Medium Risk

_parse_ensembl_cigar

Args       : none
Description: PRIVATE (internal) method - creates ungapped features from 
             internally stored cigar line in ensembl format
Returntype : list of Bio::EnsEMBL::FeaturePair
Exceptions : none
Caller     : ungapped_features
Status     : Stable

_parse_features

Arg  [1]   : listref Bio::EnsEMBL::FeaturePair $ungapped_features
Description: creates internal cigar_string and start,end hstart,hend
             entries.
Returntype : none, fills in values of self
Exceptions : argument list undergoes many sanity checks - throws under many
             invalid conditions
Caller     : new
Status     : Stable

_hit_unit

Args       : none
Description: abstract method, overwrite with something that returns
             one or three
Returntype : int 1,3
Exceptions : none
Caller     : internal
Status     : Stable

_query_unit

Args       : none
Description: abstract method, overwrite with something that returns
             one or three
Returntype : int 1,3
Exceptions : none
Caller     : internal
Status     : Stable

_mdtag_alignment_length

Arg [1]    : None
Description: return the alignment length (including indels) based on the mdtag (mdz) string
Returntype : int
Exceptions : none
Caller     : internal
Status     : Stable

_get_mdz_chunks

Arg [1]    : mdtag string - MD Z String for mismatching positions. Regex : [0-9]+(([A-Z]|\^[A-Z]+)[0-9]+)* (Refer:  SAM/BAM specification)
Description: parses the mdtag string and group it according the type
             eg: MD:Z:35^VIVALE31^GRPLIQPRRKKAYQLEHTFQGLLGKRSLFTE10 returns ['35', '^', 'VIVALE', '31', '^', 'GRPLIQPRRKKAYQLEHTFQGLLGKRSLFTE', '10']
Returntype : array of strings
Exceptions : none
Caller     : internal
Status     : Stable

_get_mdz_alignment_length

Arg [1]    : array of strings
Description: calculate the alignment length from the given chunks
Returntype : array of strings
Exceptions : none
Caller     : internal
Status     : Stable

_get_mdz_chunk_type

Arg [1]    : char
Description: get the chunk type
Returntype : string
Exceptions : none
Caller     : internal
Status     : Stable

_mdz_alignment_string

Arg [1]    : input sequence
Arg [2]    : MD Z String for mismatching positions. Regex : [0-9]+(([A-Z]|\^[A-Z]+)[0-9]+)* (Refer:  SAM/BAM specification)
             eg: MD:Z:96^RHKTDSFVGLMGKRALNS0V14
Example    : $pf->alignment_strings
Description: Allows to rebuild the alignment string of both the seq and hseq sequence
Returntype : array reference containing 2 strings
             the first corresponds to seq
             the second corresponds to hseq
Exceptions : none
Caller     : general
Status     : Stable