In any type of cell division, there is an interphase stage before the actual process of division which is a preparatory process or stage that includes different substages like G1, S, and G2. S phase is a synthesis of the cell cycle responsible for duplication or replication of the DNA.
So, at the end of the S phase, the DNA amount becomes double its initial amount and remains the same in the G2 phase. So, if the initial amount is 12 picogram then it will be double in the S phase and remain 12 in G2 as well.
Likely if you harm the ribosomes the cell will die. Cells absolutely require ribosomes for normal functioning...they are constantly replacing proteins (including enzymes and the ribosomal proteins) to keep alive.