from Bio import SeqIO

def load_genome(genome_id):
    # Load the extraterrestrial genome sequence from a specified database
    # and return the DNA sequence
    # Replace 'database' with the actual database name or API call
    genome_sequence = 'database.get_sequence(genome_id)'
    return genome_sequence

def edit_genome(genome_sequence, target_gene_sequence, modification):
    # Perform targeted gene editing using the CRISPR-Cas9 system
    # Replace the following code with the actual CRISPR-Cas9 implementation
    edited_sequence = genome_sequence.replace(target_gene_sequence, modification)
    return edited_sequence

# Example usage
genome_id = 'ET123'
target_gene_sequence = 'ATGCTGACGT'
modification = 'ATGCTGCCGT'
genome_sequence = load_genome(genome_id)
edited_sequence = edit_genome(genome_sequence, target_gene_sequence, modification)

# Output the modified genome sequence in a markdown code block
print(f"```\n{edited_sequence}\n```")