def get_fastas(fasta_file, genes=False):
    """
    >>> get_fastas('a.fasta')
    ('a.genomic.masked.fasta', 'a.features.fasta')

    >>> get_fastas('a.fasta', genes=True)
    ('a.genomic.masked.genes.fasta', False)
    """

    if not genes:
        genomic_masked = fasta_file.replace('.fa', '.genomic.masked.fa')
        features_fasta = fasta_file.replace('.fa', '.features.fa')
    else:
        genomic_masked = fasta_file.replace('.fa', '.genomic.masked.genes.fa')
        features_fasta = False #fasta_file.replace('.fa', '.genes.fa')

    return genomic_masked, features_fasta