Below is the list of tables from the database along with their columns and datatype. Need to generate an accurate SQL query for the question.
Only use the columns present in the respective table. Only use the columns which are required to generate the SQL query. Only use table joins if required and not otherwise.

### Tables ###
TABLE: CREATE TABLE table_29871617_1 ( name VARCHAR, property VARCHAR )

### Question ###
Which chromosomes have an unknown property?

### Accurate SQL ###

SELECT name FROM table_29871617_1 WHERE property = "Unknown"