Final answer:
Sister chromatids are linked together by the centromere, which is the region of a chromosome that joins them. Cohesin proteins maintain this connection until cell division occurs.
Step-by-step explanation:
Sister chromatids are linked together by a region called the centromere. The centromere is the part of a chromosome that is involved in cell division as it holds the sister chromatids together until they are separated during mitosis or meiosis. The proteins known as cohesin are responsible for holding the sister chromatids together at the centromere.
During mitosis, the nuclear envelope breaks down to allow the microtubules, which are part of the spindle apparatus, to attach to the kinetochores located at the centromeres. It is this spindle apparatus that facilitates the separation of sister chromatids later in cell division.