[BioRuby] Bio::Sequence forces a DNA sequence to lowercase?

[Gordon Robertson]

I'm new to BioRuby, so apologize for asking about something that's  
very basic, and that likely was discussed and resolved in the distant  
past.

I'm parsing PWM scan 'hits' from a report. The hit sequences have the  
form "accattAATTAt", where the uppercase letters mark the positions  
corrsponding to the five most highly conserved bases in the PWM.  
Given the output format of the PWM scanner, which I don't control, I  
need to reverse-complement the (-)-strand hits. And I want to  
preserve the uppercase characters, getting 'aTAATTaatggt' back.

I could write something to do this, but thought that this might be a  
good time to simplify things by using BioRuby. However, when I load  
BioRuby 1.2.1 into 'irb', and start to look at Bio::Sequence methods,  
I find that the example code given at http://dev.bioruby.org/wiki/en/? 
Tutorial.rd immediately forces the input sequence to lowercase -
   require 'bio'
   seq = Bio::Sequence::NA.new("atgcATGcaaaa")
  "atgcatgcaaaa"

Inspecting the list of methods available (seq.methods.sort), I see  
several standard case-control methods, but nothing that appears to  
permit me to 'lock' or 'freeze' the cases of the input sequence  
letters, in order that lowercase and uppercase letters are returned  
appropriately.

Is there such a method, or another (simple) way to have upper and  
lower case characters passed through DNA/RNA methods?

G
--
Gordon Robertson
Canada's Michael Smith Genome Sciences Centre
Vancouver BC Canada