The part labelled I in a cell is the centromere.
The centromere is a specialized region on a chromosome where the two identical sister chromatids are joined together. During cell division, the spindle fibers attach to the centromere and pull the sister chromatids apart, ensuring that each new cell receives one complete set of chromosomes. Therefore, the centromere plays a crucial role in cell division and the distribution of genetic material to the daughter cells.
The part labelled I is the________