Ace::Sequence::Feature - Examine Sequence Feature Tables
# open database connection and get an Ace::Object sequence use Ace::Sequence;
# get a megabase from the middle of chromosome I $seq = Ace::Sequence->new(-name => 'CHROMOSOME_I, -db => $db, -offset => 3_000_000, -length => 1_000_000);
# get all the homologies (a list of Ace::Sequence::Feature objs) @homol = $seq->features('Similarity');
# Get information about the first one $feature = $homol[0]; $type = $feature->type; $subtype = $feature->subtype; $start = $feature->start; $end = $feature->end; $score = $feature->score;
# Follow the target $target = $feature->info;
# print the target's start and end positions print $target->start,'-',$target->end, "\n";
Ace::Sequence::Feature is a subclass of the Ace::Sequence::Feature manpage specialized for returning information about particular features in a GFF format feature table.
You will not ordinarily create an Ace::Sequence::Feature object
directly. Instead, objects will be created in response to a feature()
call to an Ace::Sequence object. If you wish to create an
Ace::Sequence::Feature object directly, please consult the source
code for the new() method.
Most methods are inherited from Ace::Sequence. The following methods are also supported:
seqname()
$object = $feature->seqname;
Return the ACeDB Sequence object that this feature is attached to.
The return value is an Ace::Object of the Sequence class. This
corresponds to the first field of the GFF format and does not
necessarily correspond to the Ace::Sequence object from which the
feature was obtained (use source_seq()
for that).
source()
method()
subtype()
$source = $feature->source;
These three methods are all synonyms for the same thing. They return
the second field of the GFF format, called "source" in the
documentation. This is usually the method or algorithm used to
predict the feature, such as "GeneFinder" or "tRNA" scan. To avoid
ambiguity and enhance readability, the method()
and subtype()
synonyms
are also recognized.
feature()
type()
$type = $feature->type;
These two methods are also synonyms. They return the type of the
feature, such as "exon", "similarity" or "Predicted_gene". In the GFF
documentation this is called the "feature" field. For readability,
you can also use type()
to fetch the field.
abs_start()
$start = $feature->abs_start;
This method returns the absolute start of the feature within the
sequence segment indicated by seqname()
. As in the Ace::Sequence
method, use start()
to obtain the start of the feature relative to its
source.
abs_start()
$start = $feature->abs_start;
This method returns the start of the feature relative to the sequence
segment indicated by seqname()
. As in the Ace::Sequence method,
you will more usually use the inherited start()
method to obtain the
start of the feature relative to its source sequence (the
Ace::Sequence from which it was originally derived).
abs_end()
$start = $feature->abs_end;
This method returns the end of the feature relative to the sequence
segment indicated by seqname()
. As in the Ace::Sequence method,
you will more usually use the inherited end()
method to obtain the end
of the feature relative to the Ace::Sequence from which it was
derived.
score()
$score = $feature->score;
For features that are associated with a numeric score, such as similarities, this returns that value. For other features, this method returns undef.
strand()
$strand = $feature->strand;
Returns the strandedness of this feature, either "+1" or "-1". For features that are not stranded, returns 0.
reversed()
$reversed = $feature->reversed;
Returns true if the feature is reversed relative to its source sequence.
frame()
$frame = $feature->frame;
For features that have a frame, such as a predicted coding sequence, returns the frame, either 0, 1 or 2. For other features, returns undef.
group()
info()
target()
$info = $feature->info;
These methods (synonyms for one another) return an Ace::Object containing other information about the feature derived from the 8th field of the GFF format, the so-called "group" field. The type of the Ace::Object is dependent on the nature of the feature. The possibilities are shown in the table below:
Feature Type Value of Group Field ------------ -------------------- note A Text object containing the note. similarity An Ace::Sequence::Homology object containing the target and its start/stop positions.
intron An Ace::Object containing the gene from exon which the feature is derived. misc_feature
other A Text object containing the group data.
asString()
$label = $feature->asString;
Returns a human-readable identifier describing the nature of the feature. The format is:
$type:$name/$start-$end
for example:
exon:ZK154.3/1-67
This method is also called automatically when the object is treated in a string context.
the Ace manpage, the Ace::Object manpage, the Ace::Sequence manpage,the Ace::Sequence::Homol manpage, the Ace::Sequence::FeatureList manpage, GFF
Lincoln Stein <lstein@cshl.org> with extensive help from Jean Thierry-Mieg <mieg@kaa.crbm.cnrs-mop.fr>
Copyright (c) 1999, Lincoln D. Stein
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself. See DISCLAIMER.txt for disclaimers of warranty.