How does the Constitution define the roles and responsibilities of Public Service Commissions in India?
The Constitution defines the roles and responsibilities of Public Service Commissions in India as follows:

1. References to the Union Public Service Commission or a State Public Service Commission are to be construed as references to the Commission serving the needs of the Union or, as the case may be, the State as respects the particular matter in question.
2. The Chairman and other members of a Public Service Commission shall be appointed by the President for the Union Commission or a Joint Commission, and by the Governor of the State for a State Commission.
3. One-half of the members of every Public Service Commission must have held office for at least ten years either under the Government of India or under the Government of a State. Time spent holding office under the Crown in India or under the Government of an Indian State is also included in this period.
4. If the Chairman's office becomes vacant or the Chairman is unable to perform their duties due to absence or any other reason, another member of the Commission may be appointed by the President (in case of Union Commission or Joint Commission) or the Governor of the State (in case of a State Commission) to perform the Chairman's duties until the situation is resolved.