AP BIOLOGY

Detailed explanation-1: -Because each chromosome was duplicated during the S phase that occurred just before prophase I, each now consists of two sister chromatids joined at the centromere. This arrangement means that each chromosome has the shape of an X.

Detailed explanation-2: -A chromatid is one of the two identical halves of a chromosome that has been replicated in preparation for cell division. The two “sister” chromatids are joined at a constricted region of the chromosome called the centromere.

Detailed explanation-3: -DNA condenses and coils into the familiar X-shaped form of a chromosome only after it has replicated. Because DNA has already replicated, each chromosome actually consists of two identical copies. The two copies are called sister chromatids. They are attached to one another at a region called the centromere.

Detailed explanation-4: -The replicated chromosomes have an X shape and are called sister chromatids. The sister chromatids are pairs of identical copies of DNA joined at a point called the centromere.

Detailed explanation-5: -In the S phase (synthesis phase), DNA replication results in the formation of two identical copies of each chromosome-sister chromatids-that are firmly attached at the centromere region. At this stage, each chromosome is made of two sister chromatids and is a duplicated chromosome.