Swap nucleotide sequence to opposite chromosome strand

swap_strand.rb

# Swaps the nucleotide sequence to the opposite strand
#
# This means if the sequence is on the forward strand,
# then the function will return the corresponding sequence
# on the reverse strand, and vice versa.
#
# For example:
#   Original: TCCAGACAC
#   Swapped:  GTGTCTGGA
#
# @param seq [String] Original nucleotide sequence
# @return [String] Nucleotide sequence on opposite strand
def swap_strand(seq)
  seq = seq.reverse.upcase.split("")
  seq.each_with_index do |base, i|
    seq[i] = 'A' if base == 'T' 
    seq[i] = 'T' if base == 'A' 
    seq[i] = 'G' if base == 'C' 
    seq[i] = 'C' if base == 'G' 
  end 
  return seq.join("")
end