Final answer:
The two identical copies of a duplicated chromosome are called sister chromatids, and they are joined together at a region called the centromere.
Step-by-step explanation:
The two sides of a duplicated chromosome are called sister chromatids. After DNA replication, each chromosome consists of two identical copies of DNA, referred to as sister chromatids. These are attached to each other at a specific region known as the centromere. The centromere is not only a point of attachment but also contains proteins called kinetochores, which are essential during cell division for the attachment of spindle fibers that pull the sister chromatids apart.
During the S phase of the cell cycle, DNA replication occurs, and cohesin proteins bind the sister chromatids together at the centromere, ensuring they remain connected until they are separated into individual chromosomes during anaphase II of meiosis, or anaphase of mitosis. It is essential to not confuse sister chromatids with a homologous pair of chromosomes, which represent two different chromosomes inherited from each parent.