A centromere is a region of a chromosome that plays a crucial role during cell division. It is the point where two sister chromatids are joined together, forming a structure that looks like a constriction. The centromere is essential for the proper segregation of chromosomes into daughter cells, ensuring that each new cell receives the correct number of chromosomes. During the process of mitosis and meiosis, the centromere serves as the attachment site for spindle fibers, which help pull the chromatids apart. This ensures that genetic material is accurately distributed, maintaining the integrity of the organism's genome throughout generations.