Summary

Bio::Align::Utilities - A collection of utilities regarding converting
and manipulating alignment objects

Package variables

Included modules

Inherit

Exporter

Synopsis

  use Bio::Align::Utilities qw(:all);
  # %dnaseqs is a hash of CDS sequences (spliced)

  # Even if the protein alignments are local make sure the start/end
  # stored in the LocatableSeq objects are to the full length protein.
  # The CoDing Sequence that is passed in should still be the full 
  # length CDS as the nt alignment will be generated.
  #
  my $dna_aln = &aa_to_dna_aln($aa_aln,\%dnaseqs);

  # generate bootstraps
  my $replicates = &bootstrap_replicates($aln,$count);

Description

This module contains utility methods for manipulating sequence
alignments ( Bio::Align::AlignI) objects.
The aa_to_dna_aln utility is essentially the same as the mrtrans
program by Bill Pearson available at
ftp://ftp.virginia.edu/pub/fasta/other/mrtrans.shar. Of course this
is a pure-perl implementation, but just to mention that if anything
seems odd you can check the alignments generated against Bill's
program.

Methods

Methods description

 Title   : aa_to_dna_aln
 Usage   : my $dnaaln = aa_to_dna_aln($aa_aln, \%seqs);
 Function: Will convert an AA alignment to DNA space given the 
           corresponding DNA sequences.  Note that this method expects 
           the DNA sequences to be in frame +1 (GFF frame 0) as it will
           start to project into coordinates starting at the first base of 
           the DNA sequence, if this alignment represents a different 
           frame for the cDNA you will need to edit the DNA sequences
           to remove the 1st or 2nd bases (and revcom if things should be).
 Returns : Bio::Align::AlignI object 
 Args    : 2 arguments, the alignment and a hashref.
           Alignment is a Bio::Align::AlignI of amino acid sequences. 
           The hash reference should have keys which are 
           the display_ids for the aa 
           sequences in the alignment and the values are a 
           Bio::PrimarySeqI object for the corresponding 
           spliced cDNA sequence. 

 Title   : bootstrap_replicates
 Usage   : my $alns = &bootstrap_replicates($aln,100);
 Function: Generate a pseudo-replicate of the data by randomly
           sampling, with replacement, the columns from an alignment for
           the non-parametric bootstrap.
 Returns : Arrayref of Bio::SimpleAlign objects
 Args    : Bio::SimpleAlign object
           Number of replicates to generate

Methods code

BEGIN {

    use constant CODONSIZE => 3;
    $GAP = '-';
    $CODONGAP = $GAP x CODONSIZE;

}

sub aa_to_dna_aln {

    my ($aln,$dnaseqs) = @_;
    unless( defined $aln && 
	    ref($aln) &&
	    $aln->isa('Bio::Align::AlignI') ) { 
	croak('Must provide a valid Bio::Align::AlignI object as the first argument to aa_to_dna_aln, see the documentation for proper usage and the method signature');
    }
    my $alnlen = $aln->length;
    my $dnaalign = new Bio::SimpleAlign;
    $aln->map_chars('\.',$GAP);

    foreach my $seq ( $aln->each_seq ) {    
	my $aa_seqstr = $seq->seq();
	my $id = $seq->display_id;
	my $dnaseq = $dnaseqs->{$id} || $aln->throw("cannot find ".
						     $seq->display_id);
	my $start_offset = ($seq->start - 1) * CODONSIZE;

	$dnaseq = $dnaseq->seq();
	my $dnalen = $dnaseqs->{$id}->length;
	my $nt_seqstr;
	my $j = 0;
	for( my $i = 0; $i < $alnlen; $i++ ) {
	    my $char = substr($aa_seqstr,$i + $start_offset,1);	    
	    if ( $char eq $GAP || $j >= $dnalen )  { 
		$nt_seqstr .= $CODONGAP;
	    } else {
		$nt_seqstr .= substr($dnaseq,$j,CODONSIZE);
		$j += CODONSIZE;
	    }
	}
	$nt_seqstr .= $GAP x (($alnlen * 3) - length($nt_seqstr));

	my $newdna = new Bio::LocatableSeq(-display_id  => $id,
					   -alphabet    => 'dna',
					   -start       => $start_offset+1,
					   -end         => ($seq->end * 
							    CODONSIZE),
					   -strand      => 1,
					   -seq         => $nt_seqstr);    
	$dnaalign->add_seq($newdna);
    }
    return $dnaalign;

}

sub bootstrap_replicates {

   my ($aln,$count) = @_;
   $count ||= 1;
   my $alen = $aln->length;
   my (@seqs,@nm);
   $aln->set_displayname_flat(1);
   for my $s ( $aln->each_seq ) {
       push @seqs, $s->seq();
       push @nm, $s->id;
   }
   my (@alns,$i);
   while( $count-- > 0 ) {
       my @newseqs;
       for($i =0; $i < $alen; $i++ ) {
	   my $index = int(rand($alen));
	   my $c = 0;
	   for ( @seqs ) {
	       $newseqs[$c++] .= substr($_,$index,1);
	   }
       }
       my $newaln = Bio::SimpleAlign->new();
       my $i = 0;
       for my $s ( @newseqs ) {

	   $newaln->add_seq( Bio::LocatableSeq->new
			     (-start         => 1,
			      -end           => $alen,
			      -display_id    => $nm[$i++],
			      -seq           => $s));
       }
       push @alns, $newaln;
   }
   return\@ alns;

}

General documentation

User feedback is an integral part of the evolution of this and other
Bioperl modules. Send your comments and suggestions preferably to
the Bioperl mailing list. Your participation is much appreciated.

  bioperl-l@bioperl.org                  - General discussion
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Report bugs to the Bioperl bug tracking system to help us keep track
of the bugs and their resolution. Bug reports can be submitted via the
web:

  http://bugzilla.open-bio.org/

Email jason@bioperl.org

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