Bio::SeqEvolution::DNAPoint - evolve a sequence by point mutations
# $seq is a Bio::PrimarySeqI to mutate $evolve = Bio::SeqEvolution::Factory->new (-rate => 5, -seq => $seq, -identity => 50 ); $newseq = $evolve->next_seq;
Bio::SeqEvolution::DNAPoint implements the simplest evolution model: nucleotides change by point mutations, only. Transition/transversion rate of the change, rate(), can be set.
The new sequences are named with the id of the reference sequence added with a running number. Placing a new sequence into a factory to be evolved resets that counter. It can also be called directly with reset_sequence_counter.
The default sequence type returned is Bio::PrimarySeq. This can be changed to any Bio::PrimarySeqI compliant sequence class.
Internally the probability of the change of one nucleotide is mapped to scale from 0 to 100. The probability of the transition occupies range from 0 to some value. The remaining range is divided equally among the two transversion nucleotides. A random number is then generated to pick up one change.
Not that the default transition/transversion rate, 1:1, leads to observed transition/transversion ratio of 1:2 simply because there is only one transition nucleotide versus two transversion nucleotides.
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The rest of the documentation details each of the object methods. Internal methods are usually preceded with a _
Title : seq Usage : $obj->seq($newval) Function: Set the sequence object for the original sequence Returns : The sequence object Args : newvalue (optional)
Setting this will reset mutation and generated mutation counters.
Title : seq_mutated_seq Usage : $obj->set_mutated_seq($newval) Function: In case of mutating a sequence with multiple evolvers, this Returns : set_mutated_seq Args : newvalue (optional)
Title : rate Usage : $obj->rate($newval) Function: Set the transition/transversion rate. Returns : value of rate Args : newvalue (optional)
Transition/transversion ratio is an observed attribute of an sequence comparison. We are dealing here with the transition/transversion rate that we set for our model of sequence evolution.
Note that we are using standard nucleotide alphabet and that there can there is only one transition versus two possible transversions. Rate 2 is needed to have an observed transition/transversion ratio of 1.
Title : next_seq Usage : $obj->next_seq Function: Evolve the reference sequence to desired level Returns : A new sequence object mutated from the reference sequence Args : -
Title : mutate Usage : $obj->mutate Function: mutate the sequence at the given location according to the model Returns : true Args : integer, start location of the mutation, required argument
Called from next_seq().