def get_number_of_nucleotides( string ):
	""" returns the number of nucleotides ([ATCGN-]) within the string. """
	string = string.upper()
	return string.count( 'A' ) + string.count( 'T' ) + string.count( 'C' ) + string.count( 'G' ) + string.count( 'N' ) + string.count( '-' )