Most organelles show duplication in cell cycle during

Ribonuclease,a mitotic poison,inhibits the cell cycle at which stage?

Which is synthesized in $G_{1}$-phase?

$A$ plant cell has $12$ chromosomes at the end of mitosis. How many chromosomes would it have in the $G_{2}$-phase of its next cell cycle?

During which phase are chromosomes referred to as chromatin?

In which of the following cells is the cell cycle completed in $90$ minutes?