Following the end of the G2 phase of interphase, the first step of mitosis is known as prophase. The parent cell's chromosomes, which were duplicated during S phase, condense and became much smaller than they did during interphase during prophase. The two identical sister chromatids that make up each duplicated chromosome are connected at a location known as the centromere, giving these structures the appearance of being X-shaped bodies when seen under a microscope. Cohesin and condensin are two DNA-binding proteins that catalyze the condensation reaction. Condensin generates rings that coil the chromosomes into extremely compact shapes, whereas cohesin forms rings that keep the sister chromatids together.