def complement(dnaStrand):
	"""
	Complements the input DNA strand using Base pairing rules

	Input:
	dnaStrand 		DNA strand to be complemented

	Output:
	comp 			Complement of the input DNA strand
	"""
	complement = {"A":"T", "T":"A", "C":"G", "G":"C"}
	comp = ""
	for i in dnaStrand:
		comp += complement[i]
	return comp[::-1]