def fasta_sequences(fasta_filename):
    with open(fasta_filename, 'r') as fasta_file:
        header, sequence = '', ''
        for line in fasta_file:
            if line.startswith('>'):
                if header:
                    yield header, sequence
                header = line.strip()
                sequence = ''
            else:
                sequence += line.strip()
        yield header, sequence