Advanced Placement (AP) Biology Practice Exam

Which stage of mitosis does anaphase describe?

1. Separation of chromatids moving to the poles

2. Formation of a cell plate

3. Alignment of chromosomes at the equator

4. Chromosomes condensing into visible forms

The correct answer is: Separation of chromatids moving to the poles

Anaphase is characterized by the separation of sister chromatids, which are the replicated copies of each chromosome, and their movement toward opposite poles of the cell. This process is crucial for ensuring that each daughter cell receives an identical set of chromosomes during cell division. During this stage, the proteins that hold the chromatids together are cleaved, allowing the spindle fibers to pull each chromatid away, facilitating the equal distribution of genetic material. This stage follows metaphase, where chromosomes are aligned at the cell's equator, but in anaphase, the key event is the physical separation and migration to opposite ends of the dividing cell. Other stages of mitosis involve different processes, such as the formation of a cell plate during cytokinesis or the condensing of chromosomes into a visible form during prophase, but only anaphase specifically pertains to the separation of chromatids and their movement to the poles.