user: Question: Which gene has the subject number 21?
Columns: ['Gene', 'Route of administration', 'Phase', 'Subject number', 'Status']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['CFTR', 'Lung, via aerosol', 'I', '12', 'Complete']
SQL:

assistant: SELECT "Gene" FROM "Table" WHERE "Subject number" = '21';