get the reverse complement of a DNA sequence from Bio.Seq import Seq from Bio.Alphabet import generic_dna my_dna = Seq("TGCAA", generic_dna) my_dna Seq('TGCAA', DNAAlphabet()) my_dna.complement() Seq('ACGTT', DNAAlphabet()) my_dna.reverse_complement() Seq('TTGCA', DNAAlphabet()) my_dna[::-1] # reverse only Seq('AACGT', DNAAlphabet()) http://biopython.org/wiki/Seq#Complement_and_reverse_complement |