The sister chromatids separate and begin moving toward opposite poles of the cell during which phase of mitosis?

Anaphase

Explanation:

Cell cycle is divided into two main phases: i) inter-phase and ii) mitotic phase

Inter-phase is further divided into three phases named as G1, S and G2 phase, it is the phase where DNA replication and other duplication processes occurs, and in this phase cell prepare itself for division.

Mitotic phase, this phase is further divided into four sub-phases named as prophase, metaphase, anaphase and telophase.

In anphase, during cell division, sister chromatids are separated as they are pulled apart by spindle fibers towards opposite poles.